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Artificial intelligence (AI)	Computer systems that do tasks that usually need human intelligence		tech-ai-machine-learning-terms
Machine learning (ML)	Computers learning patterns from data instead of following only fixed rules		tech-ai-machine-learning-terms
Deep learning	Machine learning with many-layered neural networks		tech-ai-machine-learning-terms
Neural network	A system of connected nodes inspired loosely by brain cells		tech-ai-machine-learning-terms
Neuron (node)	A unit in a network that takes inputs and gives an output		tech-ai-machine-learning-terms
Layer	A group of nodes in a neural network		tech-ai-machine-learning-terms
Weights	Numbers in a network that are adjusted during learning		tech-ai-machine-learning-terms
Parameters	The values a model learns, such as weights		tech-ai-machine-learning-terms
Training	Teaching a model using data		tech-ai-machine-learning-terms
Training data	Examples the model learns from		tech-ai-machine-learning-terms
Test data	New examples used to check how well a model works		tech-ai-machine-learning-terms
Validation data	Data used to tune a model during development		tech-ai-machine-learning-terms
Label	The correct answer attached to an example		tech-ai-machine-learning-terms
Feature	A measurable property used as input		tech-ai-machine-learning-terms
Model	The result of training; it makes predictions		tech-ai-machine-learning-terms
Prediction (inference)	The model's output on new data		tech-ai-machine-learning-terms
Supervised learning	Learning from labeled examples		tech-ai-machine-learning-terms
Unsupervised learning	Finding patterns in unlabeled data		tech-ai-machine-learning-terms
Reinforcement learning	Learning by trial and error with rewards		tech-ai-machine-learning-terms
Classification	Sorting into categories, like cat or dog		tech-ai-machine-learning-terms
Regression	Predicting a number, like a house price		tech-ai-machine-learning-terms
Clustering	Grouping similar items together		tech-ai-machine-learning-terms
Overfitting	A model that memorizes training data and does poorly on new data		tech-ai-machine-learning-terms
Underfitting	A model too simple to capture patterns		tech-ai-machine-learning-terms
Bias (in AI)	Unfair results caused by skewed data or design		tech-ai-machine-learning-terms
Fairness	Making AI treat people equitably		tech-ai-machine-learning-terms
Algorithm	Step-by-step instructions		tech-ai-machine-learning-terms
Gradient descent	A method for adjusting weights to reduce errors		tech-ai-machine-learning-terms
Loss function	A measure of how wrong the model is		tech-ai-machine-learning-terms
Epoch	One full pass through the training data		tech-ai-machine-learning-terms
Learning rate	How big the steps are when updating weights		tech-ai-machine-learning-terms
Accuracy	The share of predictions that are correct		tech-ai-machine-learning-terms
Confusion matrix	A table of correct and wrong predictions by class		tech-ai-machine-learning-terms
Computer vision	AI that understands images and video		tech-ai-machine-learning-terms
Natural language processing (NLP)	AI that works with human language		tech-ai-machine-learning-terms
Speech recognition	Turning speech into text		tech-ai-machine-learning-terms
Text-to-speech	Turning text into spoken sound		tech-ai-machine-learning-terms
Chatbot	A program that converses with people		tech-ai-machine-learning-terms
Large language model (LLM)	A very large model trained on lots of text to predict and generate language		tech-ai-machine-learning-terms
Token	A piece of text, such as a word or part of a word, that language models process		tech-ai-machine-learning-terms
Prompt	The input or instruction given to an AI model		tech-ai-machine-learning-terms
Prompt engineering	Writing prompts to get better answers		tech-ai-machine-learning-terms
Context window	How much text a model can consider at once		tech-ai-machine-learning-terms
Transformer	A neural network design behind most modern language models		tech-ai-machine-learning-terms
Attention	A mechanism that lets a model focus on relevant parts of its input		tech-ai-machine-learning-terms
Generative AI	AI that creates new text, images, audio or code		tech-ai-machine-learning-terms
Image generation	Creating pictures from text descriptions		tech-ai-machine-learning-terms
Diffusion model	A model that creates images by gradually removing noise		tech-ai-machine-learning-terms
Hallucination	When an AI states something false as if it were true		tech-ai-machine-learning-terms
Fine-tuning	Further training a model on specialized data		tech-ai-machine-learning-terms
Pre-training	Initial training on a large general dataset		tech-ai-machine-learning-terms
Embedding	A list of numbers representing the meaning of text or images		tech-ai-machine-learning-terms
Retrieval-augmented generation (RAG)	Letting a model look up documents before answering		tech-ai-machine-learning-terms
AI agent	An AI system that can take actions toward a goal		tech-ai-machine-learning-terms
Turing test	Alan Turing's idea of judging a machine by whether it can seem human in conversation		tech-ai-machine-learning-terms
Alan Turing	British mathematician who asked 'Can machines think?' in 1950		tech-ai-machine-learning-terms
Dartmouth workshop	The 1956 meeting where the term artificial intelligence was coined		tech-ai-machine-learning-terms
Deep Blue	IBM computer that beat chess champion Garry Kasparov in 1997		tech-ai-machine-learning-terms
AlphaGo	DeepMind program that beat Go champion Lee Sedol in 2016		tech-ai-machine-learning-terms
ImageNet	A huge image dataset that sparked deep learning progress		tech-ai-machine-learning-terms
Narrow AI	AI built for specific tasks		tech-ai-machine-learning-terms
General AI (AGI)	Hypothetical AI that can do any intellectual task a human can		tech-ai-machine-learning-terms
Robotics	Building machines that sense and act		tech-ai-machine-learning-terms
Self-driving car	A vehicle that drives using sensors and AI		tech-ai-machine-learning-terms
Recommendation system	AI that suggests videos, songs or products		tech-ai-machine-learning-terms
Deepfake	A fake image or video made by AI		tech-ai-machine-learning-terms
AI ethics	Thinking about fairness, safety, privacy and responsibility in AI		tech-ai-machine-learning-terms
Privacy and AI	AI systems should protect people's personal information		tech-ai-machine-learning-terms
Human in the loop	A person reviews or guides the AI's decisions		tech-ai-machine-learning-terms
Explainability	Understanding why an AI made a decision		tech-ai-machine-learning-terms
Check AI answers	AI can be wrong, so verify important facts		tech-ai-machine-learning-terms
Algorithm	A finite list of steps that solves a problem		tech-algorithms
Big-O notation	Describes how running time or memory grows as input grows		tech-algorithms
O(1)	Constant time; stays the same as input grows		tech-algorithms
O(log n)	Logarithmic time; grows slowly, like binary search		tech-algorithms
O(n)	Linear time; grows in proportion to input size		tech-algorithms
O(n log n)	Typical of efficient sorting like merge sort		tech-algorithms
O(n squared)	Quadratic time; typical of simple nested loops		tech-algorithms
O(2 to the n)	Exponential time; becomes huge very quickly		tech-algorithms
Time complexity	How running time grows with input size		tech-algorithms
Space complexity	How memory use grows with input size		tech-algorithms
Linear search	Check each item in order until found; O(n)		tech-algorithms
Binary search	Repeatedly halve a sorted list to find an item; O(log n)		tech-algorithms
Binary search requirement	The data must be sorted		tech-algorithms
Bubble sort	Repeatedly swaps adjacent items that are out of order; O(n squared)		tech-algorithms
Selection sort	Repeatedly picks the smallest item and places it first; O(n squared)		tech-algorithms
Insertion sort	Builds a sorted list one item at a time; good for small or nearly sorted lists		tech-algorithms
Merge sort	Splits the list, sorts the halves, then merges; O(n log n)		tech-algorithms
Quick sort	Picks a pivot and partitions around it; average O(n log n)		tech-algorithms
Heap sort	Sorts using a heap; O(n log n)		tech-algorithms
Pivot	The element used to partition in quick sort		tech-algorithms
Stable sort	A sort that keeps equal items in their original order		tech-algorithms
Divide and conquer	Split a problem, solve the parts, combine the answers		tech-algorithms
Recursion	A function calling itself on smaller input		tech-algorithms
Base case	The stopping point of a recursion		tech-algorithms
Dynamic programming	Solve overlapping subproblems once and store the results		tech-algorithms
Memoization	Caching results of function calls		tech-algorithms
Greedy algorithm	Pick the best choice at each step		tech-algorithms
Brute force	Try every possibility		tech-algorithms
Backtracking	Try choices and undo them when they fail		tech-algorithms
Breadth-first search (BFS)	Explore a graph level by level using a queue		tech-algorithms
Depth-first search (DFS)	Explore a graph as deep as possible using a stack or recursion		tech-algorithms
Dijkstra's algorithm	Finds shortest paths in a weighted graph with non-negative weights		tech-algorithms
A* search	A pathfinding algorithm that uses a guess of distance to the goal		tech-algorithms
Minimum spanning tree	A tree connecting all nodes with smallest total weight		tech-algorithms
Kruskal's and Prim's	Algorithms for finding minimum spanning trees		tech-algorithms
Topological sort	Ordering tasks so each comes after its prerequisites		tech-algorithms
Hashing	Turning data into a fixed-size number for fast lookup		tech-algorithms
Collision	When two keys hash to the same spot		tech-algorithms
Euclid's algorithm	Finds the greatest common divisor using repeated remainders		tech-algorithms
Sieve of Eratosthenes	Finds all primes up to a number by crossing out multiples		tech-algorithms
Fibonacci sequence	Each number is the sum of the two before: 0, 1, 1, 2, 3, 5...		tech-algorithms
Factorial	n! is the product of all whole numbers from 1 to n		tech-algorithms
Tower of Hanoi	A puzzle that is a classic recursion example		tech-algorithms
Traveling salesman problem	Find the shortest route visiting every city once; very hard		tech-algorithms
NP-complete	A class of hard problems with no known fast solution		tech-algorithms
P vs NP	A famous open question about whether hard-to-solve problems are also easy to check		tech-algorithms
Heuristic	A practical shortcut that finds a good answer, not always the best		tech-algorithms
Pseudocode	Plain-language description of an algorithm		tech-algorithms
Invariant	A condition that stays true during an algorithm		tech-algorithms
Best case	The fastest an algorithm can run		tech-algorithms
Worst case	The slowest an algorithm can run		tech-algorithms
Average case	Typical running time over many inputs		tech-algorithms
In-place algorithm	Uses very little extra memory		tech-algorithms
Two pointers	A technique using two positions that move through data		tech-algorithms
Sliding window	A technique moving a fixed range along data		tech-algorithms
PageRank	Google's algorithm that ranks pages by links to them		tech-algorithms
Compression algorithm	Makes data smaller, like ZIP or JPEG		tech-algorithms
Lossless compression	Compression that can be exactly reversed		tech-algorithms
Lossy compression	Compression that discards some data, like JPEG		tech-algorithms
Random number generator	An algorithm that makes numbers that look random		tech-algorithms
Machine learning algorithm	An algorithm that learns patterns from data		tech-algorithms
Al-Khwarizmi	Persian mathematician whose name gave us the word algorithm		tech-algorithms
Algorithm origin	Named after a 9th-century scholar al-Khwarizmi		tech-algorithms
Binary uses which digits?	0 and 1 (base 2)		tech-binary-hex-numbers
Decimal uses which digits?	0 to 9 (base 10)		tech-binary-hex-numbers
Hexadecimal uses which digits?	0 to 9 and A to F (base 16)		tech-binary-hex-numbers
Octal uses which digits?	0 to 7 (base 8)		tech-binary-hex-numbers
Bit	A single binary digit		tech-binary-hex-numbers
Byte	8 bits		tech-binary-hex-numbers
Nibble	4 bits, one hex digit		tech-binary-hex-numbers
Place values in an 8-bit byte	128, 64, 32, 16, 8, 4, 2, 1		tech-binary-hex-numbers
Binary 0 in decimal	0		tech-binary-hex-numbers
Binary 1 in decimal	1		tech-binary-hex-numbers
Binary 10 in decimal	2		tech-binary-hex-numbers
Binary 11 in decimal	3		tech-binary-hex-numbers
Binary 100 in decimal	4		tech-binary-hex-numbers
Binary 101 in decimal	5		tech-binary-hex-numbers
Binary 110 in decimal	6		tech-binary-hex-numbers
Binary 111 in decimal	7		tech-binary-hex-numbers
Binary 1000 in decimal	8		tech-binary-hex-numbers
Binary 1001 in decimal	9		tech-binary-hex-numbers
Binary 1010 in decimal	10		tech-binary-hex-numbers
Binary 1111 in decimal	15		tech-binary-hex-numbers
Binary 10000 in decimal	16		tech-binary-hex-numbers
Binary 11111111 in decimal	255		tech-binary-hex-numbers
Binary 10101010 in decimal	170		tech-binary-hex-numbers
Binary 1100100 in decimal	100		tech-binary-hex-numbers
Binary 100000 in decimal	32		tech-binary-hex-numbers
Decimal 12 in binary	1100		tech-binary-hex-numbers
Decimal 20 in binary	10100		tech-binary-hex-numbers
Decimal 25 in binary	11001		tech-binary-hex-numbers
Decimal 50 in binary	110010		tech-binary-hex-numbers
Decimal 64 in binary	1000000		tech-binary-hex-numbers
Decimal 100 in binary	1100100		tech-binary-hex-numbers
Decimal 128 in binary	10000000		tech-binary-hex-numbers
Decimal 255 in binary	11111111		tech-binary-hex-numbers
Decimal 10 in hex	A		tech-binary-hex-numbers
Decimal 11 in hex	B		tech-binary-hex-numbers
Decimal 12 in hex	C		tech-binary-hex-numbers
Decimal 13 in hex	D		tech-binary-hex-numbers
Decimal 14 in hex	E		tech-binary-hex-numbers
Decimal 15 in hex	F		tech-binary-hex-numbers
Decimal 16 in hex	10		tech-binary-hex-numbers
Decimal 31 in hex	1F		tech-binary-hex-numbers
Decimal 32 in hex	20		tech-binary-hex-numbers
Decimal 100 in hex	64		tech-binary-hex-numbers
Decimal 255 in hex	FF		tech-binary-hex-numbers
Decimal 256 in hex	100		tech-binary-hex-numbers
Hex FF in decimal	255		tech-binary-hex-numbers
Hex 10 in decimal	16		tech-binary-hex-numbers
Hex 1A in decimal	26		tech-binary-hex-numbers
Hex 20 in decimal	32		tech-binary-hex-numbers
Hex 7F in decimal	127		tech-binary-hex-numbers
Hex 80 in decimal	128		tech-binary-hex-numbers
Binary 1111 in hex	F		tech-binary-hex-numbers
Binary 1010 in hex	A		tech-binary-hex-numbers
Binary 11110000 in hex	F0		tech-binary-hex-numbers
Hex FF in binary	11111111		tech-binary-hex-numbers
Hex 0F in binary	00001111		tech-binary-hex-numbers
Powers of 2: 2^8	256		tech-binary-hex-numbers
Powers of 2: 2^10	1,024		tech-binary-hex-numbers
Powers of 2: 2^16	65,536		tech-binary-hex-numbers
Powers of 2: 2^32	4,294,967,296		tech-binary-hex-numbers
Number of values in 1 byte	256 (0 to 255)		tech-binary-hex-numbers
Number of values with n bits	2 to the power n		tech-binary-hex-numbers
Number of values in 4 bits	16		tech-binary-hex-numbers
Largest unsigned 8-bit number	255		tech-binary-hex-numbers
Kilobyte (KB)	About 1,000 bytes (1,024 in older binary usage)		tech-binary-hex-numbers
Megabyte (MB)	About 1 million bytes		tech-binary-hex-numbers
Gigabyte (GB)	About 1 billion bytes		tech-binary-hex-numbers
Terabyte (TB)	About 1 trillion bytes		tech-binary-hex-numbers
Kibibyte, mebibyte (KiB, MiB)	Units based on exactly 1,024		tech-binary-hex-numbers
Hex color #FF0000	Red		tech-binary-hex-numbers
Hex color #00FF00	Green		tech-binary-hex-numbers
Hex color #0000FF	Blue		tech-binary-hex-numbers
Hex color #FFFFFF	White		tech-binary-hex-numbers
Hex color #000000	Black		tech-binary-hex-numbers
ASCII	A code that gives each character a number, e.g. A is 65		tech-binary-hex-numbers
ASCII 'A' in decimal	65		tech-binary-hex-numbers
ASCII 'a' in decimal	97		tech-binary-hex-numbers
ASCII '0' in decimal	48		tech-binary-hex-numbers
Unicode	A standard that gives a number to characters from all languages and emoji		tech-binary-hex-numbers
UTF-8	A common way to store Unicode characters in bytes		tech-binary-hex-numbers
Two's complement	The method computers use to store negative numbers in binary		tech-binary-hex-numbers
Binary addition: 1 + 1	10 (that is, 0 carry 1)		tech-binary-hex-numbers
Binary addition: 101 + 11	1000		tech-binary-hex-numbers
Logic gate AND	Outputs 1 only if both inputs are 1		tech-binary-hex-numbers
Logic gate OR	Outputs 1 if at least one input is 1		tech-binary-hex-numbers
Logic gate NOT	Flips the input		tech-binary-hex-numbers
Logic gate XOR	Outputs 1 if inputs differ		tech-binary-hex-numbers
Why computers use binary	Electronic switches have two states, on and off		tech-binary-hex-numbers
Scratch	A free block-based coding language made at MIT, launched in 2007		tech-block-coding-and-robotics
Block coding	Snapping blocks together instead of typing code		tech-block-coding-and-robotics
Sprite	A character or object in a Scratch project		tech-block-coding-and-robotics
Stage	The background area where sprites act		tech-block-coding-and-robotics
Costume	A picture a sprite can wear to change its look		tech-block-coding-and-robotics
Script	A stack of blocks that runs in order		tech-block-coding-and-robotics
Event block	A block that starts code, like 'when green flag clicked'		tech-block-coding-and-robotics
Motion block	A block that moves a sprite		tech-block-coding-and-robotics
Looks block	A block that changes how a sprite appears or speaks		tech-block-coding-and-robotics
Sound block	A block that plays sound		tech-block-coding-and-robotics
Control block	A block for loops and decisions		tech-block-coding-and-robotics
Sensing block	A block that checks for touching, keys or mouse		tech-block-coding-and-robotics
Operator block	A block for math and comparing		tech-block-coding-and-robotics
Variable	A named box that holds a number or text		tech-block-coding-and-robotics
Loop	Repeating blocks		tech-block-coding-and-robotics
Forever loop	Repeats without stopping		tech-block-coding-and-robotics
Repeat 10 loop	Repeats 10 times		tech-block-coding-and-robotics
If block	Does something only when a condition is true		tech-block-coding-and-robotics
If-else block	Does one thing if true and another if false		tech-block-coding-and-robotics
Broadcast	Sends a message to other scripts or sprites		tech-block-coding-and-robotics
Clone	A copy of a sprite made while the project runs		tech-block-coding-and-robotics
Coordinates	The x and y numbers that tell where a sprite is		tech-block-coding-and-robotics
x position	How far left or right a sprite is		tech-block-coding-and-robotics
y position	How far up or down a sprite is		tech-block-coding-and-robotics
Direction	The angle a sprite is facing		tech-block-coding-and-robotics
Remix	Making a copy of someone's project to change		tech-block-coding-and-robotics
Debugging	Finding and fixing mistakes in code		tech-block-coding-and-robotics
Bug	A mistake in code		tech-block-coding-and-robotics
Sequence	Steps in the right order		tech-block-coding-and-robotics
Algorithm	Step-by-step instructions		tech-block-coding-and-robotics
Unplugged coding	Learning coding ideas without a computer		tech-block-coding-and-robotics
Pseudocode	Code ideas written in plain words		tech-block-coding-and-robotics
Event	Something that happens, like a click		tech-block-coding-and-robotics
Input	What you give to a program		tech-block-coding-and-robotics
Output	What a program shows or does		tech-block-coding-and-robotics
Function	A named group of blocks you can reuse		tech-block-coding-and-robotics
Custom block	Your own block made from other blocks		tech-block-coding-and-robotics
Hour of Code	A worldwide event that introduces coding in one hour		tech-block-coding-and-robotics
Code.org	A nonprofit that offers free coding lessons		tech-block-coding-and-robotics
Robot	A machine that can sense and act		tech-block-coding-and-robotics
Sensor	A part that detects things like light, touch or distance		tech-block-coding-and-robotics
Motor	A part that makes things move		tech-block-coding-and-robotics
Actuator	A part that makes a robot do something		tech-block-coding-and-robotics
Microcontroller	A tiny computer that controls a device		tech-block-coding-and-robotics
micro:bit	A small programmable board with lights, buttons and sensors		tech-block-coding-and-robotics
Arduino	A microcontroller board used in projects		tech-block-coding-and-robotics
Raspberry Pi	A small low-cost computer		tech-block-coding-and-robotics
LED	A small light that glows when electricity flows through it		tech-block-coding-and-robotics
Servo	A motor that turns to a set angle		tech-block-coding-and-robotics
Ultrasonic sensor	Measures distance using sound		tech-block-coding-and-robotics
Line-following robot	A robot that follows a line using sensors		tech-block-coding-and-robotics
Obstacle avoidance	A robot turns to avoid hitting things		tech-block-coding-and-robotics
Autonomous	Working by itself without being controlled		tech-block-coding-and-robotics
Remote control	Controlling a device from a distance		tech-block-coding-and-robotics
Circuit	A closed path electricity flows through		tech-block-coding-and-robotics
Battery	Stores energy to power a circuit		tech-block-coding-and-robotics
Switch	A part that opens or closes a circuit		tech-block-coding-and-robotics
Conductor	A material that lets electricity flow, like copper		tech-block-coding-and-robotics
Insulator	A material that stops electricity, like rubber		tech-block-coding-and-robotics
Prototype	A first working model		tech-block-coding-and-robotics
Design process	Ask, imagine, plan, create, test, improve		tech-block-coding-and-robotics
Engineer	A person who designs and builds solutions		tech-block-coding-and-robotics
Computational thinking	Solving problems with steps, patterns and breaking things down		tech-block-coding-and-robotics
Decompose	Break a big problem into smaller parts		tech-block-coding-and-robotics
Pattern	Something that repeats		tech-block-coding-and-robotics
Abstraction	Ignoring details to focus on what matters		tech-block-coding-and-robotics
Maze challenge	A common puzzle for practicing sequences and loops		tech-block-coding-and-robotics
Algorithm	A step-by-step set of instructions to solve a problem		tech-coding-vocabulary
Program	A set of instructions a computer follows		tech-coding-vocabulary
Code	Instructions written in a programming language		tech-coding-vocabulary
Programming language	A language for telling computers what to do		tech-coding-vocabulary
Programmer (developer)	A person who writes code		tech-coding-vocabulary
Source code	Human-readable code a programmer writes		tech-coding-vocabulary
Compiler	Translates a whole program into machine code before running		tech-coding-vocabulary
Interpreter	Reads and runs code line by line		tech-coding-vocabulary
Syntax	The grammar rules of a language		tech-coding-vocabulary
Syntax error	A mistake in following those rules		tech-coding-vocabulary
Bug	An error in a program		tech-coding-vocabulary
Debugging	Finding and fixing bugs		tech-coding-vocabulary
Logic error	Code that runs but gives the wrong result		tech-coding-vocabulary
Runtime error	An error that occurs while the program runs		tech-coding-vocabulary
Variable	A named container that stores a value		tech-coding-vocabulary
Constant	A value that does not change		tech-coding-vocabulary
Data type	The kind of value, like number or text		tech-coding-vocabulary
Integer	A whole number		tech-coding-vocabulary
Float	A number with a decimal point		tech-coding-vocabulary
String	Text in quotation marks		tech-coding-vocabulary
Boolean	A value that is true or false		tech-coding-vocabulary
Array (list)	An ordered collection of items		tech-coding-vocabulary
Dictionary (object, map)	A collection of key-value pairs		tech-coding-vocabulary
Operator	A symbol that does something with values, like + or ==		tech-coding-vocabulary
Expression	Code that produces a value		tech-coding-vocabulary
Statement	A single instruction		tech-coding-vocabulary
Assignment	Storing a value in a variable		tech-coding-vocabulary
Comparison	Checking how values relate, such as equal or greater than		tech-coding-vocabulary
Conditional	Code that runs only if a condition is true		tech-coding-vocabulary
If statement	Runs code when a condition is true		tech-coding-vocabulary
Else	Runs code when the if condition is false		tech-coding-vocabulary
Loop	Code that repeats		tech-coding-vocabulary
For loop	Repeats a set number of times or through a collection		tech-coding-vocabulary
While loop	Repeats while a condition is true		tech-coding-vocabulary
Infinite loop	A loop that never ends		tech-coding-vocabulary
Iteration	One pass through a loop		tech-coding-vocabulary
Function	A reusable block of code with a name		tech-coding-vocabulary
Parameter	A variable named in a function definition		tech-coding-vocabulary
Argument	The actual value passed into a function		tech-coding-vocabulary
Return value	The result a function gives back		tech-coding-vocabulary
Call a function	Run it		tech-coding-vocabulary
Scope	Where in the code a variable can be used		tech-coding-vocabulary
Global variable	A variable accessible everywhere		tech-coding-vocabulary
Local variable	A variable accessible only inside its function		tech-coding-vocabulary
Recursion	A function that calls itself		tech-coding-vocabulary
Base case	The stopping condition of a recursive function		tech-coding-vocabulary
Object	A bundle of data and functions		tech-coding-vocabulary
Class	A blueprint for creating objects		tech-coding-vocabulary
Method	A function that belongs to an object		tech-coding-vocabulary
Property (attribute)	A value that belongs to an object		tech-coding-vocabulary
Inheritance	A class gets features from another class		tech-coding-vocabulary
Encapsulation	Keeping data and methods together and hiding details		tech-coding-vocabulary
Polymorphism	Different objects responding to the same call in their own way		tech-coding-vocabulary
Library	Reusable code written by others		tech-coding-vocabulary
Framework	A structure of code that guides how you build apps		tech-coding-vocabulary
API	Application programming interface: rules for programs to talk to each other		tech-coding-vocabulary
Module	A file of code that can be imported		tech-coding-vocabulary
Package	A bundle of modules		tech-coding-vocabulary
Comment	A note in code ignored by the computer		tech-coding-vocabulary
Indentation	Spaces at the start of a line showing structure		tech-coding-vocabulary
Input	Data given to a program		tech-coding-vocabulary
Output	Data a program produces		tech-coding-vocabulary
Event	An action like a click that a program responds to		tech-coding-vocabulary
Pseudocode	Plain-language outline of code		tech-coding-vocabulary
Flowchart	A diagram showing the steps of an algorithm		tech-coding-vocabulary
Sequence	Steps run in order		tech-coding-vocabulary
Selection	Choosing which code runs based on a condition		tech-coding-vocabulary
Decomposition	Breaking a big problem into smaller parts		tech-coding-vocabulary
Abstraction	Hiding details to focus on what matters		tech-coding-vocabulary
Pattern recognition	Spotting similarities to solve problems		tech-coding-vocabulary
Computational thinking	Problem solving with decomposition, patterns, abstraction and algorithms		tech-coding-vocabulary
IDE	Integrated development environment, a code editor with tools		tech-coding-vocabulary
Version control	A system that tracks changes to code		tech-coding-vocabulary
Open source	Software whose code anyone can view and use		tech-coding-vocabulary
Ada Lovelace	Wrote what many call the first computer program, in 1843		tech-coding-vocabulary
CPU (processor)	The brain of the computer that runs instructions		tech-computer-parts
Core (CPU)	One processing unit inside a CPU		tech-computer-parts
Clock speed	How fast a CPU runs, measured in gigahertz (GHz)		tech-computer-parts
RAM	Fast temporary memory for programs in use; cleared when power is off		tech-computer-parts
ROM	Memory that keeps its contents without power		tech-computer-parts
Hard drive (HDD)	Storage that uses spinning magnetic disks		tech-computer-parts
SSD	Storage with no moving parts that uses flash memory; faster than a hard drive		tech-computer-parts
Motherboard	The main circuit board that connects all parts		tech-computer-parts
GPU (graphics card)	Processor that draws images and video and speeds up graphics		tech-computer-parts
Power supply (PSU)	Converts wall power into power the computer can use		tech-computer-parts
Case (tower)	The box that holds the computer parts		tech-computer-parts
Cooling fan	Moves air to keep parts from overheating		tech-computer-parts
Heat sink	Metal part that draws heat away from the CPU		tech-computer-parts
BIOS / UEFI	Basic software that starts up the computer's hardware		tech-computer-parts
Chipset	Chips on the motherboard that manage data between parts		tech-computer-parts
Expansion slot (PCIe)	A slot for adding cards like graphics cards		tech-computer-parts
Sound card	Handles audio input and output		tech-computer-parts
Network card (NIC)	Connects the computer to a network		tech-computer-parts
Optical drive	Reads CDs, DVDs and Blu-ray discs		tech-computer-parts
Monitor	A screen that shows what the computer displays		tech-computer-parts
Keyboard	Input device with keys for typing		tech-computer-parts
Mouse	A pointing device you move and click		tech-computer-parts
Touchpad	A touch-sensitive pad on a laptop that moves the pointer		tech-computer-parts
Touchscreen	A screen that senses touch		tech-computer-parts
Scanner	Copies paper pages into digital images		tech-computer-parts
Printer	Puts digital documents onto paper		tech-computer-parts
3D printer	Builds objects layer by layer from plastic or other materials		tech-computer-parts
Speakers	Output devices that play sound		tech-computer-parts
Microphone	Input device that captures sound		tech-computer-parts
Webcam	A small camera for video calls		tech-computer-parts
Headphones	Speakers worn on the ears		tech-computer-parts
Joystick	Input device for controlling games		tech-computer-parts
Game controller	Handheld input device for games		tech-computer-parts
Stylus	A pen-like tool for touchscreens		tech-computer-parts
Barcode scanner	Reads codes printed as stripes		tech-computer-parts
Input device	Hardware that sends information into the computer		tech-computer-parts
Output device	Hardware that presents information from the computer		tech-computer-parts
Storage device	Hardware that keeps data for later		tech-computer-parts
USB port	A common connector for plugging in devices		tech-computer-parts
USB flash drive (thumb drive)	A small portable storage stick		tech-computer-parts
HDMI	A cable that carries video and audio to a screen		tech-computer-parts
Ethernet port	A port for a wired network cable		tech-computer-parts
Wi-Fi	Wireless networking		tech-computer-parts
Bluetooth	Short-range wireless connection for devices like headphones		tech-computer-parts
SD card	A small memory card used in cameras		tech-computer-parts
External hard drive	A storage device outside the computer connected by a cable		tech-computer-parts
Battery	Stores power for laptops and phones		tech-computer-parts
Charger	Supplies power to a battery		tech-computer-parts
Laptop	A portable computer with a built-in screen and keyboard		tech-computer-parts
Desktop	A computer meant to stay at a desk		tech-computer-parts
Tablet	A flat touchscreen computer		tech-computer-parts
Smartphone	A phone that works like a small computer		tech-computer-parts
Server	A computer that provides services to other computers		tech-computer-parts
Supercomputer	An extremely fast computer for huge calculations		tech-computer-parts
Microcontroller	A small computer chip in a device, like in a toaster or Arduino		tech-computer-parts
Raspberry Pi	A tiny low-cost computer board		tech-computer-parts
Arduino	An open-source microcontroller board for projects		tech-computer-parts
Circuit board	A board with printed paths connecting electronic parts		tech-computer-parts
Transistor	A tiny switch inside chips		tech-computer-parts
Microchip (integrated circuit)	A tiny piece of silicon holding millions or billions of transistors		tech-computer-parts
Silicon	The material most computer chips are made from		tech-computer-parts
Bit	The smallest unit of data, a 0 or 1		tech-computer-parts
Byte	8 bits		tech-computer-parts
Peripheral	Any device connected to a computer		tech-computer-parts
Port	A socket for connecting devices		tech-computer-parts
Driver	Software that lets the computer talk to a device		tech-computer-parts
Firmware	Software built into hardware		tech-computer-parts
Ada Lovelace	Wrote notes in 1843 with what is often called the first computer program, for Babbage's Analytical Engine		tech-computer-scientists-and-history
Charles Babbage	Designed the Analytical Engine, an early mechanical computer idea, in the 1830s		tech-computer-scientists-and-history
Alan Turing	British mathematician who defined the Turing machine and helped break the Enigma code		tech-computer-scientists-and-history
Turing machine	An abstract model of computation described by Turing in 1936		tech-computer-scientists-and-history
Grace Hopper	American Navy officer who helped create the first compiler and the COBOL language		tech-computer-scientists-and-history
John von Neumann	Described the stored-program computer architecture		tech-computer-scientists-and-history
Claude Shannon	Founded information theory in 1948 and popularized the word bit		tech-computer-scientists-and-history
Katherine Johnson	NASA mathematician whose calculations helped astronauts reach orbit and the Moon		tech-computer-scientists-and-history
Margaret Hamilton	Led software development for Apollo's guidance computers		tech-computer-scientists-and-history
Dorothy Vaughan	NASA mathematician who became a leader in programming (FORTRAN) at Langley		tech-computer-scientists-and-history
Tim Berners-Lee	Invented the World Wide Web in 1989		tech-computer-scientists-and-history
Vint Cerf and Bob Kahn	Designed the TCP/IP protocols of the internet		tech-computer-scientists-and-history
Dennis Ritchie	Created the C language and co-created Unix		tech-computer-scientists-and-history
Ken Thompson	Co-creator of Unix		tech-computer-scientists-and-history
Linus Torvalds	Created the Linux kernel (1991) and Git (2005)		tech-computer-scientists-and-history
Guido van Rossum	Created Python		tech-computer-scientists-and-history
Brendan Eich	Created JavaScript in 1995		tech-computer-scientists-and-history
James Gosling	Led the creation of Java		tech-computer-scientists-and-history
Bjarne Stroustrup	Created C++		tech-computer-scientists-and-history
Yukihiro Matsumoto	Created Ruby		tech-computer-scientists-and-history
Bill Gates	Co-founded Microsoft in 1975		tech-computer-scientists-and-history
Paul Allen	Co-founded Microsoft		tech-computer-scientists-and-history
Steve Jobs	Co-founded Apple in 1976		tech-computer-scientists-and-history
Steve Wozniak	Designed the Apple I and II computers		tech-computer-scientists-and-history
Larry Page and Sergey Brin	Founded Google in 1998		tech-computer-scientists-and-history
Mark Zuckerberg	Co-founded Facebook in 2004		tech-computer-scientists-and-history
Jeff Bezos	Founded Amazon in 1994		tech-computer-scientists-and-history
Douglas Engelbart	Invented the computer mouse; demonstrated it in 1968		tech-computer-scientists-and-history
Doug Engelbart's 1968 demo	Called the Mother of All Demos; showed the mouse, video calls and hypertext		tech-computer-scientists-and-history
Ivan Sutherland	Created Sketchpad (1963), an early graphics program		tech-computer-scientists-and-history
Alan Kay	Pioneer of object-oriented programming and the personal computer		tech-computer-scientists-and-history
Donald Knuth	Wrote The Art of Computer Programming		tech-computer-scientists-and-history
Edsger Dijkstra	Created a famous shortest-path algorithm		tech-computer-scientists-and-history
Barbara Liskov	Computer scientist who won the Turing Award for work on data abstraction		tech-computer-scientists-and-history
Radia Perlman	Invented the spanning-tree protocol for networks		tech-computer-scientists-and-history
Fei-Fei Li	Computer scientist who helped create ImageNet		tech-computer-scientists-and-history
Geoffrey Hinton	Pioneer of neural networks and deep learning		tech-computer-scientists-and-history
Yann LeCun	Pioneer of convolutional neural networks		tech-computer-scientists-and-history
Yoshua Bengio	Pioneer of deep learning		tech-computer-scientists-and-history
Turing Award	The top prize in computer science, named for Alan Turing		tech-computer-scientists-and-history
ENIAC	One of the first general-purpose electronic computers, completed in 1945		tech-computer-scientists-and-history
Colossus	British code-breaking computer used in World War II		tech-computer-scientists-and-history
Transistor	Invented in 1947 at Bell Labs		tech-computer-scientists-and-history
Integrated circuit	Chip with many components, invented in the late 1950s		tech-computer-scientists-and-history
Microprocessor	A whole CPU on one chip; Intel 4004 came out in 1971		tech-computer-scientists-and-history
ARPANET	Early network that sent its first message in 1969		tech-computer-scientists-and-history
First email	Sent by Ray Tomlinson in 1971		tech-computer-scientists-and-history
Personal computer	Home computers became popular in the late 1970s and 1980s		tech-computer-scientists-and-history
Apple II	A popular early personal computer from 1977		tech-computer-scientists-and-history
IBM PC	Introduced in 1981		tech-computer-scientists-and-history
Macintosh	Apple computer launched in 1984 with a graphical interface		tech-computer-scientists-and-history
Windows 95	Microsoft system that made the Start menu famous		tech-computer-scientists-and-history
World Wide Web goes public	1991		tech-computer-scientists-and-history
Mosaic browser	Early graphical web browser from 1993		tech-computer-scientists-and-history
Google founded	1998		tech-computer-scientists-and-history
Wikipedia launched	2001		tech-computer-scientists-and-history
YouTube founded	2005		tech-computer-scientists-and-history
iPhone introduced	2007		tech-computer-scientists-and-history
Smartphone age	Phones became pocket computers after 2007		tech-computer-scientists-and-history
Cloud computing	Rented online computing, which grew in the late 2000s		tech-computer-scientists-and-history
Bitcoin created	2009 by a person or group known as Satoshi Nakamoto		tech-computer-scientists-and-history
ChatGPT released	November 2022		tech-computer-scientists-and-history
Moore's law	The observation that chip transistor counts double about every two years		tech-computer-scientists-and-history
Gordon Moore	Co-founder of Intel who described Moore's law in 1965		tech-computer-scientists-and-history
Hedy Lamarr	Actress and inventor who co-developed frequency hopping, an idea used in modern wireless		tech-computer-scientists-and-history
Mary Allen Wilkes	Programmer of the LINC, an early personal computer, in the 1960s		tech-computer-scientists-and-history
Jean Bartik	One of the six original ENIAC programmers		tech-computer-scientists-and-history
Annie Easley	NASA computer scientist who worked on rocket software		tech-computer-scientists-and-history
Mark Dean	IBM engineer who helped design the original IBM PC and holds key patents in PC technology		tech-computer-scientists-and-history
Gladys West	Mathematician whose work contributed to GPS		tech-computer-scientists-and-history
color	Sets the text color		tech-css-properties
background-color	Sets the background color		tech-css-properties
background-image	Sets a background picture		tech-css-properties
font-family	Chooses the typeface		tech-css-properties
font-size	Sets the text size		tech-css-properties
font-weight	Sets how bold text is		tech-css-properties
font-style	Sets italic or normal		tech-css-properties
text-align	Aligns text left, center, right or justify		tech-css-properties
text-decoration	Adds underline, overline or line-through		tech-css-properties
text-transform	Changes case: uppercase, lowercase, capitalize		tech-css-properties
line-height	Sets space between lines of text		tech-css-properties
letter-spacing	Sets space between letters		tech-css-properties
width	Sets the width of an element		tech-css-properties
height	Sets the height of an element		tech-css-properties
max-width	Sets the largest width allowed		tech-css-properties
min-height	Sets the smallest height allowed		tech-css-properties
margin	Space outside an element's border		tech-css-properties
padding	Space inside an element between content and border		tech-css-properties
border	Draws a line around an element		tech-css-properties
border-radius	Rounds the corners of an element		tech-css-properties
box-shadow	Adds a shadow around an element		tech-css-properties
text-shadow	Adds a shadow to text		tech-css-properties
opacity	Sets transparency from 0 to 1		tech-css-properties
display	Sets how an element is shown: block, inline, flex, grid, none		tech-css-properties
display: none	Hides an element and its space		tech-css-properties
visibility: hidden	Hides an element but keeps its space		tech-css-properties
position	Sets how an element is positioned: static, relative, absolute, fixed, sticky		tech-css-properties
position: relative	Positions an element compared to its normal spot		tech-css-properties
position: absolute	Positions an element relative to its nearest positioned parent		tech-css-properties
position: fixed	Keeps an element in place when scrolling		tech-css-properties
position: sticky	Sticks an element once you scroll to it		tech-css-properties
top, right, bottom, left	Offsets for positioned elements		tech-css-properties
z-index	Sets stacking order of overlapping elements		tech-css-properties
float	Pushes an element to the left or right so text wraps around it		tech-css-properties
overflow	Controls what happens when content is too big		tech-css-properties
box-sizing: border-box	Includes padding and border in an element's width		tech-css-properties
Flexbox (display: flex)	A layout system for rows or columns		tech-css-properties
flex-direction	Sets row or column in flexbox		tech-css-properties
justify-content	Aligns flex items along the main axis		tech-css-properties
align-items	Aligns flex items along the cross axis		tech-css-properties
flex-wrap	Lets flex items wrap to the next line		tech-css-properties
gap	Space between flex or grid items		tech-css-properties
flex-grow	How much an item grows to fill space		tech-css-properties
Grid (display: grid)	A two-dimensional layout system		tech-css-properties
grid-template-columns	Defines the columns of a grid		tech-css-properties
grid-template-rows	Defines the rows of a grid		tech-css-properties
grid-column	Places an item across columns		tech-css-properties
Selector	The part of CSS that picks which elements to style		tech-css-properties
Element selector	Targets tags, like p { }		tech-css-properties
Class selector	Targets by class, like .box { }		tech-css-properties
ID selector	Targets by ID, like #main { }		tech-css-properties
Descendant selector	Targets elements inside others, like nav a { }		tech-css-properties
Child selector	Targets direct children only, like ul > li { }		tech-css-properties
Universal selector	* targets all elements		tech-css-properties
Pseudo-class	A state selector like :hover or :focus		tech-css-properties
Pseudo-element	Selects part of an element like ::before or ::first-line		tech-css-properties
Specificity	The rule deciding which style wins when rules conflict		tech-css-properties
Cascade	Styles are combined in order and importance		tech-css-properties
Inheritance	Some properties pass down from parent to child		tech-css-properties
!important	Makes a rule override others, to be used rarely		tech-css-properties
Media query	A rule that applies styles for certain screen sizes		tech-css-properties
Responsive design	Pages that adapt to different screen sizes		tech-css-properties
Pixels (px)	A fixed unit of size		tech-css-properties
em unit	A size relative to the parent's font size		tech-css-properties
rem unit	A size relative to the root font size		tech-css-properties
Percent (%)	A size relative to the parent		tech-css-properties
vh and vw	1% of the viewport height or width		tech-css-properties
Hex color	A color written as #RRGGBB, like #FF0000		tech-css-properties
rgb()	A color written with red, green and blue values		tech-css-properties
hsl()	A color written with hue, saturation and lightness		tech-css-properties
transition	Animates changes between styles		tech-css-properties
transform	Moves, rotates, scales or skews an element		tech-css-properties
animation	Applies keyframe animation		tech-css-properties
@keyframes	Defines the steps of an animation		tech-css-properties
CSS stands for	Cascading Style Sheets		tech-css-properties
CSS variable	A reusable value set with --name and used with var(--name)		tech-css-properties
cursor	Changes the mouse pointer style		tech-css-properties
list-style	Changes bullets or numbers in lists		tech-css-properties
Cybersecurity	Protecting computers, networks and data from attack		tech-cybersecurity-basics
CIA triad	Confidentiality, Integrity, Availability		tech-cybersecurity-basics
Confidentiality	Only authorized people can see the data		tech-cybersecurity-basics
Integrity	Data is accurate and has not been tampered with		tech-cybersecurity-basics
Availability	Systems and data are usable when needed		tech-cybersecurity-basics
Threat	Something that could cause harm		tech-cybersecurity-basics
Vulnerability	A weakness that can be exploited		tech-cybersecurity-basics
Exploit	A way to take advantage of a vulnerability		tech-cybersecurity-basics
Risk	The chance a threat uses a vulnerability and causes harm		tech-cybersecurity-basics
Malware	Harmful software		tech-cybersecurity-basics
Virus	Malware that attaches to files and spreads		tech-cybersecurity-basics
Worm	Malware that spreads by itself over networks		tech-cybersecurity-basics
Trojan horse	Malware disguised as something useful		tech-cybersecurity-basics
Ransomware	Malware that locks files and demands payment		tech-cybersecurity-basics
Spyware	Software that secretly watches what you do		tech-cybersecurity-basics
Adware	Software that shows unwanted ads		tech-cybersecurity-basics
Keylogger	Malware that records keystrokes		tech-cybersecurity-basics
Botnet	A network of infected computers controlled by an attacker		tech-cybersecurity-basics
Phishing	Fake messages that trick you into giving information		tech-cybersecurity-basics
Spear phishing	Phishing aimed at a specific person		tech-cybersecurity-basics
Smishing	Phishing by text message		tech-cybersecurity-basics
Social engineering	Tricking people rather than breaking technology		tech-cybersecurity-basics
Pretexting	Inventing a story to gain trust		tech-cybersecurity-basics
Brute force attack	Trying many passwords until one works		tech-cybersecurity-basics
Dictionary attack	Trying common words as passwords		tech-cybersecurity-basics
Credential stuffing	Reusing leaked passwords on other sites		tech-cybersecurity-basics
DDoS attack	Flooding a site with traffic to knock it offline		tech-cybersecurity-basics
Man-in-the-middle attack	An attacker secretly intercepts communication		tech-cybersecurity-basics
SQL injection	Sneaking harmful database commands into input		tech-cybersecurity-basics
Cross-site scripting (XSS)	Injecting harmful scripts into web pages		tech-cybersecurity-basics
Zero-day	A vulnerability unknown to the maker, with no fix yet		tech-cybersecurity-basics
Patch	An update that fixes a vulnerability		tech-cybersecurity-basics
Software updates	Install them promptly to close security holes		tech-cybersecurity-basics
Strong password	Long and unique, not reused		tech-cybersecurity-basics
Passphrase	A long password made of several words		tech-cybersecurity-basics
Password manager	A tool that stores unique passwords safely		tech-cybersecurity-basics
Multi-factor authentication	Requiring two or more proofs of identity		tech-cybersecurity-basics
Authentication	Proving who you are		tech-cybersecurity-basics
Authorization	What you're allowed to do after logging in		tech-cybersecurity-basics
Biometrics	Using fingerprints or faces to identify you		tech-cybersecurity-basics
Encryption	Scrambling data so only holders of a key can read it		tech-cybersecurity-basics
Decryption	Unscrambling encrypted data		tech-cybersecurity-basics
Symmetric encryption	Uses the same key to lock and unlock		tech-cybersecurity-basics
Asymmetric encryption	Uses a public key to lock and a private key to unlock		tech-cybersecurity-basics
Public key	A key you can share		tech-cybersecurity-basics
Private key	A key you keep secret		tech-cybersecurity-basics
Hash	A fixed-length fingerprint of data, hard to reverse		tech-cybersecurity-basics
Salt	Random data added to a password before hashing		tech-cybersecurity-basics
Digital signature	Proof that a message came from a certain sender		tech-cybersecurity-basics
Certificate	A digital ID that proves a website is who it claims to be		tech-cybersecurity-basics
HTTPS	Secure web connections that use encryption		tech-cybersecurity-basics
VPN	Creates an encrypted tunnel for your traffic		tech-cybersecurity-basics
Firewall	Blocks unwanted network traffic		tech-cybersecurity-basics
Antivirus	Software that detects malware		tech-cybersecurity-basics
Intrusion detection system	Monitors a network for suspicious activity		tech-cybersecurity-basics
Sandbox	A safe isolated space to run untrusted code		tech-cybersecurity-basics
Backup	A copy of data kept separately		tech-cybersecurity-basics
3-2-1 backup rule	3 copies, 2 types of media, 1 offsite		tech-cybersecurity-basics
Least privilege	Giving users only the access they need		tech-cybersecurity-basics
Defense in depth	Using many layers of protection		tech-cybersecurity-basics
Penetration testing	Authorized hacking to find weaknesses		tech-cybersecurity-basics
White hat hacker	An ethical hacker who helps improve security		tech-cybersecurity-basics
Black hat hacker	A criminal hacker		tech-cybersecurity-basics
Gray hat hacker	A hacker between ethical and criminal		tech-cybersecurity-basics
Bug bounty	A reward for responsibly reporting security flaws		tech-cybersecurity-basics
Data breach	When private data is exposed		tech-cybersecurity-basics
Identity theft	Using someone's personal information without permission		tech-cybersecurity-basics
Public Wi-Fi risk	Others may snoop; avoid sensitive logins		tech-cybersecurity-basics
Suspicious email clues	Urgent threats, odd sender, bad links, requests for passwords		tech-cybersecurity-basics
Hover before clicking	Check where a link really goes		tech-cybersecurity-basics
Never share	Passwords or verification codes with anyone		tech-cybersecurity-basics
Incident response	The plan for handling a security event		tech-cybersecurity-basics
Cipher	A method of encrypting text		tech-cybersecurity-basics
Caesar cipher	Shifts each letter by a fixed number		tech-cybersecurity-basics
Enigma	A cipher machine used by Germany in World War II		tech-cybersecurity-basics
Kerckhoffs's principle	A system should be secure even if everything but the key is public		tech-cybersecurity-basics
Data structure	A way of organizing data so it can be used efficiently		tech-data-structures
Array	A fixed-size list of items stored in order, accessed by index		tech-data-structures
Index	The position number of an item in an array, starting at 0 in most languages		tech-data-structures
Dynamic array	An array that grows automatically, like a Python list		tech-data-structures
Linked list	Items (nodes) linked by pointers, each pointing to the next		tech-data-structures
Node	A piece of a linked structure holding data and links		tech-data-structures
Singly linked list	Each node points only to the next		tech-data-structures
Doubly linked list	Each node points to both the next and the previous		tech-data-structures
Pointer (reference)	A value that tells where another value is stored		tech-data-structures
Stack	A last-in, first-out (LIFO) structure		tech-data-structures
Push	Add an item to a stack		tech-data-structures
Pop	Remove the top item from a stack		tech-data-structures
Peek	Look at the top item without removing it		tech-data-structures
Queue	A first-in, first-out (FIFO) structure		tech-data-structures
Enqueue	Add an item to the back of a queue		tech-data-structures
Dequeue	Remove the item at the front of a queue		tech-data-structures
Deque	A double-ended queue; add or remove at either end		tech-data-structures
Priority queue	A queue where higher priority items leave first		tech-data-structures
Hash table (hash map)	Stores key-value pairs for fast lookup using a hash function		tech-data-structures
Hash function	Converts a key into a number to find its slot		tech-data-structures
Set	A collection of unique items		tech-data-structures
Dictionary (map)	A collection of key-value pairs		tech-data-structures
Tuple	An ordered, unchangeable group of values		tech-data-structures
Tree	A hierarchy of nodes with a root and branches		tech-data-structures
Root	The top node of a tree		tech-data-structures
Leaf	A node with no children		tech-data-structures
Parent and child	A node and the nodes directly below it		tech-data-structures
Depth	How many steps a node is from the root		tech-data-structures
Height of a tree	The longest path from the root to a leaf		tech-data-structures
Binary tree	A tree in which each node has at most two children		tech-data-structures
Binary search tree (BST)	A binary tree where left values are smaller and right values are larger		tech-data-structures
Balanced tree	A tree whose branches are roughly equal in height		tech-data-structures
AVL tree	A self-balancing binary search tree		tech-data-structures
Heap	A tree-based structure where the parent is always larger (or smaller) than its children		tech-data-structures
Min-heap	The smallest element is at the top		tech-data-structures
Max-heap	The largest element is at the top		tech-data-structures
Trie	A tree for storing words by their letters		tech-data-structures
Graph	Nodes (vertices) connected by edges		tech-data-structures
Vertex	A node in a graph		tech-data-structures
Edge	A connection between two vertices		tech-data-structures
Directed graph	Edges have a direction		tech-data-structures
Undirected graph	Edges go both ways		tech-data-structures
Weighted graph	Edges have values like distance or cost		tech-data-structures
Adjacency list	Graph stored as a list of neighbors for each vertex		tech-data-structures
Adjacency matrix	Graph stored as a grid showing which vertices connect		tech-data-structures
Cycle	A path that returns to its starting vertex		tech-data-structures
Tree vs graph	A tree is a graph with no cycles that is connected		tech-data-structures
Record (struct)	A bundle of named fields		tech-data-structures
String	A sequence of characters		tech-data-structures
Matrix	A grid of values in rows and columns		tech-data-structures
2D array	An array of arrays, like a grid		tech-data-structures
Stack use	Undo buttons, function calls, browser back		tech-data-structures
Queue use	Print jobs, task scheduling		tech-data-structures
Hash table use	Fast lookups, caches, counting		tech-data-structures
Tree use	File systems, search, hierarchies		tech-data-structures
Graph use	Maps, social networks, the internet		tech-data-structures
Access time of an array by index	O(1)		tech-data-structures
Search time in an unsorted array	O(n)		tech-data-structures
Insertion at the front of a linked list	O(1)		tech-data-structures
Search time in a balanced BST	O(log n)		tech-data-structures
Average lookup in a hash table	O(1)		tech-data-structures
Call stack	The stack that tracks which function is running		tech-data-structures
Stack overflow	When the call stack runs out of space, often from endless recursion		tech-data-structures
Abstract data type (ADT)	A description of what a structure does, not how		tech-data-structures
Circular buffer	A fixed-size queue that wraps around		tech-data-structures
Bloom filter	A compact structure that tells if an item might be in a set		tech-data-structures
Union-find	A structure that tracks groups of connected items		tech-data-structures
Immutable	Cannot be changed after creation		tech-data-structures
Mutable	Can be changed after creation		tech-data-structures
.txt	Plain text file		tech-file-types-and-formats
.doc / .docx	Microsoft Word document		tech-file-types-and-formats
.pdf	Portable Document Format, looks the same on any device		tech-file-types-and-formats
.rtf	Rich Text Format, text with simple formatting		tech-file-types-and-formats
.odt	OpenDocument text file		tech-file-types-and-formats
.xls / .xlsx	Microsoft Excel spreadsheet		tech-file-types-and-formats
.csv	Comma-separated values, a simple data table in text		tech-file-types-and-formats
.ppt / .pptx	Microsoft PowerPoint presentation		tech-file-types-and-formats
.key	Apple Keynote presentation		tech-file-types-and-formats
.pages	Apple Pages document		tech-file-types-and-formats
.jpg / .jpeg	Compressed photo image		tech-file-types-and-formats
.png	Image with lossless compression and transparency		tech-file-types-and-formats
.gif	Image format that supports simple animation		tech-file-types-and-formats
.bmp	Uncompressed bitmap image		tech-file-types-and-formats
.svg	Scalable vector graphics, sharp at any size		tech-file-types-and-formats
.webp	Modern web image format		tech-file-types-and-formats
.heic	Apple's efficient photo format		tech-file-types-and-formats
.tiff	High-quality image format		tech-file-types-and-formats
.psd	Adobe Photoshop file		tech-file-types-and-formats
.ai	Adobe Illustrator file		tech-file-types-and-formats
.mp3	Compressed audio		tech-file-types-and-formats
.wav	Uncompressed audio		tech-file-types-and-formats
.aac	Compressed audio format used by Apple		tech-file-types-and-formats
.flac	Lossless compressed audio		tech-file-types-and-formats
.ogg	Open audio format		tech-file-types-and-formats
.midi / .mid	File with music notes instead of sound		tech-file-types-and-formats
.mp4	Common video format		tech-file-types-and-formats
.mov	Apple QuickTime video		tech-file-types-and-formats
.avi	Older Microsoft video format		tech-file-types-and-formats
.mkv	Flexible video container format		tech-file-types-and-formats
.webm	Open video format for the web		tech-file-types-and-formats
.zip	Compressed archive of files		tech-file-types-and-formats
.rar	Compressed archive format		tech-file-types-and-formats
.7z	7-Zip compressed archive		tech-file-types-and-formats
.tar.gz	Compressed archive common on Linux		tech-file-types-and-formats
.exe	Windows program		tech-file-types-and-formats
.msi	Windows installer		tech-file-types-and-formats
.dmg	Mac disk image used for installing apps		tech-file-types-and-formats
.app	Mac application		tech-file-types-and-formats
.apk	Android app package		tech-file-types-and-formats
.ipa	iOS app package		tech-file-types-and-formats
.iso	Disk image of a disc		tech-file-types-and-formats
.html / .htm	Web page		tech-file-types-and-formats
.css	Stylesheet for web pages		tech-file-types-and-formats
.js	JavaScript code		tech-file-types-and-formats
.json	JavaScript Object Notation, a common data format		tech-file-types-and-formats
.xml	Extensible Markup Language, structured data		tech-file-types-and-formats
.py	Python code		tech-file-types-and-formats
.java	Java source code		tech-file-types-and-formats
.class	Compiled Java code		tech-file-types-and-formats
.c / .cpp	C and C++ source code		tech-file-types-and-formats
.cs	C# source code		tech-file-types-and-formats
.php	PHP script		tech-file-types-and-formats
.rb	Ruby script		tech-file-types-and-formats
.sql	SQL database commands		tech-file-types-and-formats
.db / .sqlite	Database file		tech-file-types-and-formats
.md	Markdown text file		tech-file-types-and-formats
.yml / .yaml	Human-readable configuration data		tech-file-types-and-formats
.sh	Shell script		tech-file-types-and-formats
.bat	Windows batch file		tech-file-types-and-formats
.ini / .cfg	Configuration file		tech-file-types-and-formats
.log	Log file recording events		tech-file-types-and-formats
.tmp	Temporary file		tech-file-types-and-formats
.bak	Backup file		tech-file-types-and-formats
.dll	Windows dynamic link library		tech-file-types-and-formats
.sys	System file		tech-file-types-and-formats
.ttf / .otf	Font files		tech-file-types-and-formats
.epub	E-book format		tech-file-types-and-formats
.ics	Calendar event file		tech-file-types-and-formats
.vcf	Contact card file		tech-file-types-and-formats
.torrent	File used by peer-to-peer sharing software		tech-file-types-and-formats
File extension	The letters after the dot that suggest the file type		tech-file-types-and-formats
Filename	The name before the extension		tech-file-types-and-formats
Folder (directory)	A container for files		tech-file-types-and-formats
Path	The location of a file, such as C:\Users\Sam\file.txt		tech-file-types-and-formats
Operating system	Software that manages a computer, like Windows, macOS, Linux, Android, iOS		tech-file-types-and-formats
Git	A version control system that tracks changes to files		tech-git-commands
Repository (repo)	A project folder tracked by Git		tech-git-commands
Create a new repository	git init		tech-git-commands
Copy a repository	git clone <url>		tech-git-commands
See what has changed	git status		tech-git-commands
Stage a file	git add file.txt		tech-git-commands
Stage everything	git add .		tech-git-commands
Commit staged changes	git commit -m 'message'		tech-git-commands
Commit	A saved snapshot of the project		tech-git-commands
Commit message	A short note describing the change		tech-git-commands
Staging area (index)	Where changes wait before committing		tech-git-commands
Working directory	Your project files as they currently are		tech-git-commands
View history	git log		tech-git-commands
View history briefly	git log --oneline		tech-git-commands
See changes not yet staged	git diff		tech-git-commands
See staged changes	git diff --staged		tech-git-commands
Branch	A separate line of work		tech-git-commands
List branches	git branch		tech-git-commands
Create a branch	git branch name		tech-git-commands
Switch branch	git switch name		tech-git-commands
Create and switch to a branch	git switch -c name		tech-git-commands
Old switch command	git checkout name		tech-git-commands
Merge a branch	git merge name		tech-git-commands
Merge conflict	When Git can't combine changes automatically		tech-git-commands
Resolve a conflict	Edit the file, remove markers, then add and commit		tech-git-commands
Delete a branch	git branch -d name		tech-git-commands
main branch	The default primary branch		tech-git-commands
Remote	A copy of the repository on a server		tech-git-commands
Origin	The usual name of the main remote		tech-git-commands
Add a remote	git remote add origin <url>		tech-git-commands
Show remotes	git remote -v		tech-git-commands
Send commits to a remote	git push		tech-git-commands
First push of a branch	git push -u origin name		tech-git-commands
Get new commits from remote	git fetch		tech-git-commands
Fetch and merge from remote	git pull		tech-git-commands
Undo staging of a file	git restore --staged file		tech-git-commands
Discard local changes to a file	git restore file		tech-git-commands
Undo the last commit but keep changes	git reset --soft HEAD~1		tech-git-commands
Make a new commit that undoes a commit	git revert <hash>		tech-git-commands
Fix the last commit message	git commit --amend		tech-git-commands
Temporarily save changes	git stash		tech-git-commands
Bring back stashed changes	git stash pop		tech-git-commands
Tag a commit	git tag v1.0		tech-git-commands
HEAD	A pointer to the current commit		tech-git-commands
Hash	The unique ID of a commit		tech-git-commands
Rebase	Move commits onto a new base for a straight history		tech-git-commands
Cherry-pick	Copy one commit onto another branch		tech-git-commands
Fork	Your own copy of someone else's repository		tech-git-commands
Pull request (PR)	A request to merge your branch into another		tech-git-commands
Code review	Teammates read and comment on changes		tech-git-commands
GitHub	A website hosting Git repositories		tech-git-commands
GitLab	Another site for hosting Git repositories		tech-git-commands
Issue	A task or bug report on GitHub		tech-git-commands
Clone vs fork	Clone copies to your computer; fork copies to your account		tech-git-commands
README	A file describing a project		tech-git-commands
License	A file saying how others may use the code		tech-git-commands
Gitignore	A file listing what Git should not track		tech-git-commands
Linus Torvalds	Created Git in 2005		tech-git-commands
Diff	The difference between two versions of files		tech-git-commands
Blame	git blame shows who last changed each line		tech-git-commands
Bisect	git bisect finds the commit that introduced a bug		tech-git-commands
Detached HEAD	Being on a commit that is not at the tip of a branch		tech-git-commands
Force push	git push --force overwrites remote history; use with great care		tech-git-commands
Never commit	Passwords, tokens or secret keys		tech-git-commands
Commit often	Small commits are easier to understand		tech-git-commands
Feature branch	A branch made for one new feature		tech-git-commands
Continuous integration (CI)	Tests run automatically when code is pushed		tech-git-commands
<html>	The root element that wraps the whole page		tech-html-tags
<!DOCTYPE html>	Declares the page uses modern HTML5		tech-html-tags
<head>	Holds information about the page, not shown on screen		tech-html-tags
<title>	The page title shown in the browser tab		tech-html-tags
<meta>	Metadata about the page, like character set		tech-html-tags
<link>	Links to outside files such as stylesheets		tech-html-tags
<style>	Holds CSS written inside the page		tech-html-tags
<script>	Holds or loads JavaScript		tech-html-tags
<body>	The visible content of the page		tech-html-tags
<h1>	The main heading, the largest		tech-html-tags
<h2> to <h6>	Smaller headings		tech-html-tags
<p>	A paragraph of text		tech-html-tags
<br>	A line break		tech-html-tags
<hr>	A horizontal line dividing content		tech-html-tags
<a href='url'>	A link to another page		tech-html-tags
<img src='pic.jpg' alt='description'>	Shows an image; alt describes it		tech-html-tags
<strong>	Important text, usually bold		tech-html-tags
<em>	Emphasized text, usually italic		tech-html-tags
<b>	Bold text without extra importance		tech-html-tags
<i>	Italic text		tech-html-tags
<u>	Underlined text		tech-html-tags
<mark>	Highlighted text		tech-html-tags
<code>	A short piece of computer code		tech-html-tags
<pre>	Preformatted text that keeps spaces and line breaks		tech-html-tags
<blockquote>	A long quotation		tech-html-tags
<ul>	An unordered (bulleted) list		tech-html-tags
<ol>	An ordered (numbered) list		tech-html-tags
<li>	One item in a list		tech-html-tags
<dl>, <dt>, <dd>	A description list, its term, and its description		tech-html-tags
<table>	A table		tech-html-tags
<tr>	A table row		tech-html-tags
<td>	A table cell		tech-html-tags
<th>	A table header cell		tech-html-tags
<thead>, <tbody>, <tfoot>	Parts of a table		tech-html-tags
<div>	A generic block container		tech-html-tags
<span>	A generic inline container		tech-html-tags
<header>	Introductory content or navigation area		tech-html-tags
<nav>	A group of navigation links		tech-html-tags
<main>	The main content of the page		tech-html-tags
<section>	A themed group of content		tech-html-tags
<article>	Independent content like a blog post		tech-html-tags
<aside>	Side content related to the main content		tech-html-tags
<footer>	Footer content, such as copyright		tech-html-tags
<figure> and <figcaption>	An image or diagram with a caption		tech-html-tags
<form>	A form to collect information		tech-html-tags
<input>	A field where users type or choose		tech-html-tags
<label>	A text label for a form control		tech-html-tags
<textarea>	A large multi-line text box		tech-html-tags
<select> and <option>	A dropdown menu and its choices		tech-html-tags
<button>	A clickable button		tech-html-tags
<fieldset> and <legend>	Groups form controls with a title		tech-html-tags
<audio>	Plays sound		tech-html-tags
<video>	Plays video		tech-html-tags
<source>	Specifies a media file for audio or video		tech-html-tags
<canvas>	A drawing area for graphics scripts		tech-html-tags
<svg>	Vector graphics drawn in code		tech-html-tags
<iframe>	Embeds another page inside the page		tech-html-tags
<details> and <summary>	A show/hide widget with a visible summary		tech-html-tags
<abbr>	An abbreviation		tech-html-tags
<time>	A date or time		tech-html-tags
<sup> and <sub>	Superscript and subscript text		tech-html-tags
Attribute	Extra information in a tag, like href or src		tech-html-tags
id attribute	A unique name for one element		tech-html-tags
class attribute	A name shared by many elements for styling		tech-html-tags
alt attribute	Text describing an image, for screen readers		tech-html-tags
href attribute	The link destination		tech-html-tags
src attribute	The source file of an image or script		tech-html-tags
target='_blank'	Opens a link in a new tab		tech-html-tags
type attribute (input)	Chooses the control type: text, checkbox, number and so on		tech-html-tags
placeholder attribute	Hint text shown in an empty input		tech-html-tags
required attribute	The form field must be filled in		tech-html-tags
Comment in HTML	<!-- comment -->		tech-html-tags
Self-closing (void) tags	Tags with no closing tag, like <br>, <img>, <input>		tech-html-tags
Nesting	Putting tags inside other tags		tech-html-tags
HTML stands for	HyperText Markup Language		tech-html-tags
Internet	A worldwide network of connected computers		tech-internet-basics-and-safety
World Wide Web	Pages and sites you view in a browser, which run on the internet		tech-internet-basics-and-safety
Web browser	Software for viewing websites, like Chrome, Safari or Firefox		tech-internet-basics-and-safety
Website	A collection of linked web pages		tech-internet-basics-and-safety
Web page	A single document on a website		tech-internet-basics-and-safety
URL	A web address		tech-internet-basics-and-safety
Domain name	The name of a site, like example.com		tech-internet-basics-and-safety
Top-level domain	The ending of a domain name, like .com, .org or .edu		tech-internet-basics-and-safety
Link (hyperlink)	Text or a picture you click to go to another page		tech-internet-basics-and-safety
Homepage	The main page of a website		tech-internet-basics-and-safety
Search engine	A website that finds pages for your search words		tech-internet-basics-and-safety
Keyword	A word used to search		tech-internet-basics-and-safety
Bookmark	A saved shortcut to a web page		tech-internet-basics-and-safety
Tab	One page open inside a browser window		tech-internet-basics-and-safety
Cookie	A small file a website saves in your browser		tech-internet-basics-and-safety
Cache	Stored copies of pages to load faster		tech-internet-basics-and-safety
Browsing history	A list of pages you visited		tech-internet-basics-and-safety
Incognito (private) mode	Browsing that doesn't save history on your device		tech-internet-basics-and-safety
Download	Copy a file from the internet to your device		tech-internet-basics-and-safety
Upload	Send a file from your device to the internet		tech-internet-basics-and-safety
Stream	Watch or listen online without saving the whole file		tech-internet-basics-and-safety
Email	Electronic mail		tech-internet-basics-and-safety
Attachment	A file sent along with an email		tech-internet-basics-and-safety
Spam	Unwanted junk email or messages		tech-internet-basics-and-safety
Social media	Websites and apps for sharing and connecting		tech-internet-basics-and-safety
Blog	A website with regularly posted entries		tech-internet-basics-and-safety
Wiki	A site anyone can edit, like Wikipedia		tech-internet-basics-and-safety
Podcast	An audio show you can download or stream		tech-internet-basics-and-safety
Cloud storage	Keeping files on internet servers		tech-internet-basics-and-safety
Wi-Fi	Wireless internet connection		tech-internet-basics-and-safety
Router	A device that sends data between your devices and the internet		tech-internet-basics-and-safety
Modem	A device that connects your home to your internet provider		tech-internet-basics-and-safety
ISP	Internet service provider, the company giving you internet		tech-internet-basics-and-safety
Bandwidth	How much data can be sent in a given time		tech-internet-basics-and-safety
Broadband	High-speed internet		tech-internet-basics-and-safety
Ping	The time a signal takes to travel to a server and back		tech-internet-basics-and-safety
Password	A secret code to protect an account		tech-internet-basics-and-safety
Strong password	Long, unique and hard to guess		tech-internet-basics-and-safety
Password manager	An app that stores your passwords safely		tech-internet-basics-and-safety
Two-factor authentication (2FA)	Using two proofs of identity, like a password and a code		tech-internet-basics-and-safety
Phishing	Fake messages that try to trick you into giving information		tech-internet-basics-and-safety
Scam	A trick to steal money or information		tech-internet-basics-and-safety
Malware	Harmful software		tech-internet-basics-and-safety
Virus	Malware that spreads by copying itself		tech-internet-basics-and-safety
Antivirus	Software that finds and removes malware		tech-internet-basics-and-safety
Firewall	A shield that blocks unwanted connections		tech-internet-basics-and-safety
VPN	A virtual private network that encrypts your connection		tech-internet-basics-and-safety
Encryption	Scrambling data so only the right person can read it		tech-internet-basics-and-safety
HTTPS	Secure web connection; look for the lock icon		tech-internet-basics-and-safety
HTTP	The protocol for sending web pages, without encryption		tech-internet-basics-and-safety
Privacy settings	Controls for who sees your information		tech-internet-basics-and-safety
Personal information	Details like name, address and school; keep private		tech-internet-basics-and-safety
Digital footprint	The record of what you do online		tech-internet-basics-and-safety
Cyberbullying	Bullying that happens online		tech-internet-basics-and-safety
Block	Stop a person from contacting you		tech-internet-basics-and-safety
Report	Tell the site about harmful content		tech-internet-basics-and-safety
Misinformation	False information		tech-internet-basics-and-safety
Fact-check	Look up whether something is true		tech-internet-basics-and-safety
Source	Where information comes from		tech-internet-basics-and-safety
Credible source	A trustworthy source		tech-internet-basics-and-safety
Copyright	The law that protects creators' work		tech-internet-basics-and-safety
Creative Commons	Licenses that let creators share work with permission		tech-internet-basics-and-safety
Citing a source	Giving credit for information you use		tech-internet-basics-and-safety
Netiquette	Polite online behavior		tech-internet-basics-and-safety
Digital citizenship	Using technology safely and respectfully		tech-internet-basics-and-safety
Screen time	Time spent on screens		tech-internet-basics-and-safety
Sharing rule	If you wouldn't say it to a person's face, don't post it		tech-internet-basics-and-safety
Tim Berners-Lee	Invented the World Wide Web in 1989		tech-internet-basics-and-safety
First website	Went online in 1991 at CERN		tech-internet-basics-and-safety
ARPANET	Early network (1969) that grew into the internet		tech-internet-basics-and-safety
Print to the console	console.log('Hi')		tech-javascript-basics
Declare a changeable variable	let x = 5;		tech-javascript-basics
Declare a constant	const PI = 3.14;		tech-javascript-basics
Old way to declare a variable	var x = 5;		tech-javascript-basics
Single-line comment	// comment		tech-javascript-basics
Strict equality	a === b		tech-javascript-basics
Strict inequality	a !== b		tech-javascript-basics
Logical and	a && b		tech-javascript-basics
Logical or	a || b		tech-javascript-basics
Logical not	!a		tech-javascript-basics
Remainder	7 % 2		tech-javascript-basics
Exponent	2 ** 3		tech-javascript-basics
Increment	i++		tech-javascript-basics
If statement	if (x > 3) { }		tech-javascript-basics
Else if	else if (x === 3) { }		tech-javascript-basics
Ternary operator	cond ? a : b		tech-javascript-basics
Switch statement	switch (x) { case 1: break; }		tech-javascript-basics
For loop	for (let i = 0; i < 5; i++) { }		tech-javascript-basics
For...of loop	for (const item of arr) { }		tech-javascript-basics
For...in loop	for (const key in obj) { }		tech-javascript-basics
While loop	while (x < 10) { }		tech-javascript-basics
Function declaration	function add(a, b) { return a + b; }		tech-javascript-basics
Arrow function	const add = (a, b) => a + b;		tech-javascript-basics
Anonymous function	function () { }		tech-javascript-basics
Make an array	const arr = [1, 2, 3];		tech-javascript-basics
Add to end of array	arr.push(4)		tech-javascript-basics
Remove last item	arr.pop()		tech-javascript-basics
Add to start	arr.unshift(0)		tech-javascript-basics
Remove first item	arr.shift()		tech-javascript-basics
Array length	arr.length		tech-javascript-basics
Loop over each item	arr.forEach(x => ...)		tech-javascript-basics
Transform every item	arr.map(x => x * 2)		tech-javascript-basics
Keep items that pass a test	arr.filter(x => x > 2)		tech-javascript-basics
Combine into one value	arr.reduce((sum, x) => sum + x, 0)		tech-javascript-basics
Find first match	arr.find(x => x > 2)		tech-javascript-basics
Does the array include a value?	arr.includes(3)		tech-javascript-basics
Sort an array (numbers)	arr.sort((a, b) => a - b)		tech-javascript-basics
Join array into a string	arr.join(', ')		tech-javascript-basics
Make an object	const o = { name: 'Sam', age: 9 };		tech-javascript-basics
Read an object property	o.name or o['name']		tech-javascript-basics
Get keys of an object	Object.keys(o)		tech-javascript-basics
Template literal	`Hello ${name}`		tech-javascript-basics
String length	s.length		tech-javascript-basics
String uppercase	s.toUpperCase()		tech-javascript-basics
Split a string	s.split(' ')		tech-javascript-basics
Convert to number	Number('5') or parseInt('5')		tech-javascript-basics
Check not a number	isNaN(x)		tech-javascript-basics
Random number 0 to 1	Math.random()		tech-javascript-basics
Round down	Math.floor(3.7)		tech-javascript-basics
Round	Math.round(3.5)		tech-javascript-basics
Absolute value	Math.abs(-3)		tech-javascript-basics
Larger of values	Math.max(1, 5)		tech-javascript-basics
Undefined	A variable that has not been given a value		tech-javascript-basics
Null	An intentional empty value		tech-javascript-basics
typeof operator	typeof x		tech-javascript-basics
Select an element by ID	document.getElementById('id')		tech-javascript-basics
Select with a CSS selector	document.querySelector('.cls')		tech-javascript-basics
Change text of an element	el.textContent = 'Hi'		tech-javascript-basics
Change style	el.style.color = 'red'		tech-javascript-basics
Add a class	el.classList.add('on')		tech-javascript-basics
Listen for a click	el.addEventListener('click', fn)		tech-javascript-basics
Wait before running code	setTimeout(fn, 1000)		tech-javascript-basics
Repeat code over time	setInterval(fn, 1000)		tech-javascript-basics
Fetch data from a URL	fetch(url)		tech-javascript-basics
Parse JSON text	JSON.parse(text)		tech-javascript-basics
Convert to JSON text	JSON.stringify(obj)		tech-javascript-basics
Promise	An object for a value that will be available later		tech-javascript-basics
async / await	Syntax for writing asynchronous code that reads in order		tech-javascript-basics
Try/catch	try { } catch (e) { }		tech-javascript-basics
Class definition	class Dog { constructor(name) { this.name = name; } }		tech-javascript-basics
this keyword	Refers to the current object		tech-javascript-basics
Import a module	import x from './x.js';		tech-javascript-basics
Export a function	export function f() { }		tech-javascript-basics
Spread operator	[...arr]		tech-javascript-basics
Destructuring	const { a, b } = obj;		tech-javascript-basics
JavaScript's creator	Brendan Eich, in 1995		tech-javascript-basics
Is JavaScript the same as Java?	No, they are different languages		tech-javascript-basics
Copy	Ctrl+C (Windows) or Cmd+C (Mac)		tech-keyboard-shortcuts
Cut	Ctrl+X or Cmd+X		tech-keyboard-shortcuts
Paste	Ctrl+V or Cmd+V		tech-keyboard-shortcuts
Undo	Ctrl+Z or Cmd+Z		tech-keyboard-shortcuts
Redo	Ctrl+Y or Cmd+Shift+Z		tech-keyboard-shortcuts
Select all	Ctrl+A or Cmd+A		tech-keyboard-shortcuts
Save	Ctrl+S or Cmd+S		tech-keyboard-shortcuts
Save as	Ctrl+Shift+S or Cmd+Shift+S		tech-keyboard-shortcuts
Open	Ctrl+O or Cmd+O		tech-keyboard-shortcuts
New document or window	Ctrl+N or Cmd+N		tech-keyboard-shortcuts
Print	Ctrl+P or Cmd+P		tech-keyboard-shortcuts
Find	Ctrl+F or Cmd+F		tech-keyboard-shortcuts
Find and replace	Ctrl+H (Windows) or Cmd+Option+F (Mac, in some apps)		tech-keyboard-shortcuts
Bold	Ctrl+B or Cmd+B		tech-keyboard-shortcuts
Italic	Ctrl+I or Cmd+I		tech-keyboard-shortcuts
Underline	Ctrl+U or Cmd+U		tech-keyboard-shortcuts
Close the window or tab	Ctrl+W or Cmd+W		tech-keyboard-shortcuts
Quit the app (Mac)	Cmd+Q		tech-keyboard-shortcuts
Close the window (Windows)	Alt+F4		tech-keyboard-shortcuts
Reopen closed browser tab	Ctrl+Shift+T or Cmd+Shift+T		tech-keyboard-shortcuts
New browser tab	Ctrl+T or Cmd+T		tech-keyboard-shortcuts
Switch to next browser tab	Ctrl+Tab		tech-keyboard-shortcuts
Switch to a specific tab	Ctrl+1 to 8 (or Cmd+1 to 8)		tech-keyboard-shortcuts
Refresh a web page	Ctrl+R or F5 (Windows); Cmd+R (Mac)		tech-keyboard-shortcuts
Go back in the browser	Alt+Left Arrow or Cmd+Left Arrow		tech-keyboard-shortcuts
Go forward in the browser	Alt+Right Arrow or Cmd+Right Arrow		tech-keyboard-shortcuts
Focus the address bar	Ctrl+L or Cmd+L		tech-keyboard-shortcuts
Bookmark the page	Ctrl+D or Cmd+D		tech-keyboard-shortcuts
Zoom in	Ctrl+Plus or Cmd+Plus		tech-keyboard-shortcuts
Zoom out	Ctrl+Minus or Cmd+Minus		tech-keyboard-shortcuts
Reset zoom	Ctrl+0 or Cmd+0		tech-keyboard-shortcuts
Switch between open apps (Windows)	Alt+Tab		tech-keyboard-shortcuts
Switch between open apps (Mac)	Cmd+Tab		tech-keyboard-shortcuts
Show the desktop (Windows)	Windows key+D		tech-keyboard-shortcuts
Open Task Manager (Windows)	Ctrl+Shift+Esc		tech-keyboard-shortcuts
Force Quit (Mac)	Cmd+Option+Esc		tech-keyboard-shortcuts
Lock the screen (Windows)	Windows key+L		tech-keyboard-shortcuts
Lock the screen (Mac)	Control+Cmd+Q		tech-keyboard-shortcuts
Screenshot (Windows)	Windows key+Shift+S		tech-keyboard-shortcuts
Screenshot of whole screen (Mac)	Cmd+Shift+3		tech-keyboard-shortcuts
Screenshot of a selection (Mac)	Cmd+Shift+4		tech-keyboard-shortcuts
Open Spotlight search (Mac)	Cmd+Space		tech-keyboard-shortcuts
Open the Start menu / search (Windows)	Windows key		tech-keyboard-shortcuts
Open File Explorer (Windows)	Windows key+E		tech-keyboard-shortcuts
Emoji picker (Windows)	Windows key+Period		tech-keyboard-shortcuts
Emoji picker (Mac)	Control+Cmd+Space		tech-keyboard-shortcuts
Select a word	Double-click it		tech-keyboard-shortcuts
Select a whole paragraph	Triple-click it		tech-keyboard-shortcuts
Select the word to the left	Ctrl+Shift+Left Arrow (Windows) or Option+Shift+Left Arrow (Mac)		tech-keyboard-shortcuts
Move to the start of a line	Home (Windows) or Cmd+Left (Mac)		tech-keyboard-shortcuts
Move to the end of a line	End (Windows) or Cmd+Right (Mac)		tech-keyboard-shortcuts
Move to the start of a document	Ctrl+Home or Cmd+Up		tech-keyboard-shortcuts
Move to the end of a document	Ctrl+End or Cmd+Down		tech-keyboard-shortcuts
Delete the previous word	Ctrl+Backspace or Option+Delete		tech-keyboard-shortcuts
Rename a file	F2 (Windows) or Return (Mac)		tech-keyboard-shortcuts
Delete a file (to trash)	Delete key or Cmd+Delete		tech-keyboard-shortcuts
Permanently delete a file (Windows)	Shift+Delete		tech-keyboard-shortcuts
Open the Run box (Windows)	Windows key+R		tech-keyboard-shortcuts
Copy a file path	Right-click and choose Copy as path, in Windows		tech-keyboard-shortcuts
Insert a line break within a paragraph	Shift+Enter		tech-keyboard-shortcuts
Caps Lock	A key that makes all letters capital		tech-keyboard-shortcuts
Shift key	Hold to type capitals and symbols		tech-keyboard-shortcuts
Tab key	Moves to the next field or indents		tech-keyboard-shortcuts
Esc key	Cancels or exits		tech-keyboard-shortcuts
Function keys (F1 to F12)	Special keys for actions, such as F1 for help		tech-keyboard-shortcuts
Print Screen key	Captures the screen on Windows		tech-keyboard-shortcuts
Home row	The row of keys ASDF JKL; where fingers rest when typing		tech-keyboard-shortcuts
F and J keys	Have bumps to help you find the home row		tech-keyboard-shortcuts
QWERTY	The most common keyboard layout, named for the top row of letters		tech-keyboard-shortcuts
Right-click equivalent on Mac trackpad	Two-finger tap or Control+click		tech-keyboard-shortcuts
ls	List files and folders		tech-linux-commands
ls -l	List with details like size and permissions		tech-linux-commands
ls -a	List all files including hidden ones		tech-linux-commands
cd folder	Change into a folder		tech-linux-commands
cd ..	Go up one folder		tech-linux-commands
cd ~ or cd	Go to your home folder		tech-linux-commands
pwd	Print the current working directory		tech-linux-commands
mkdir name	Make a new folder		tech-linux-commands
rmdir name	Remove an empty folder		tech-linux-commands
touch file	Create an empty file or update its timestamp		tech-linux-commands
cp a b	Copy a file		tech-linux-commands
cp -r a b	Copy a folder and its contents		tech-linux-commands
mv a b	Move or rename a file		tech-linux-commands
rm file	Delete a file (no undo)		tech-linux-commands
rm -r folder	Delete a folder and contents (dangerous)		tech-linux-commands
cat file	Show a file's contents		tech-linux-commands
less file	View a file one page at a time		tech-linux-commands
head file	Show the first lines of a file		tech-linux-commands
tail file	Show the last lines of a file		tech-linux-commands
tail -f file	Follow a file as new lines are added		tech-linux-commands
echo text	Print text		tech-linux-commands
grep pattern file	Search for text in a file		tech-linux-commands
grep -r pattern .	Search recursively through folders		tech-linux-commands
find . -name 'x'	Find files by name		tech-linux-commands
wc -l file	Count lines in a file		tech-linux-commands
sort file	Sort lines		tech-linux-commands
uniq	Remove repeated adjacent lines		tech-linux-commands
diff a b	Show differences between two files		tech-linux-commands
chmod	Change file permissions		tech-linux-commands
chmod +x file	Make a file executable		tech-linux-commands
chown	Change the owner of a file		tech-linux-commands
sudo	Run a command with administrator privileges		tech-linux-commands
su	Switch user		tech-linux-commands
whoami	Show the current user name		tech-linux-commands
man command	Show the manual for a command		tech-linux-commands
--help	Show brief help for a command		tech-linux-commands
history	Show previous commands		tech-linux-commands
clear	Clear the terminal screen		tech-linux-commands
Ctrl+C	Stop the running command		tech-linux-commands
Ctrl+D	End input or log out		tech-linux-commands
Ctrl+L	Clear the screen		tech-linux-commands
Up arrow	Recall the previous command		tech-linux-commands
Tab key	Auto-complete a name		tech-linux-commands
ps	Show running processes		tech-linux-commands
top or htop	Show live process and resource usage		tech-linux-commands
kill PID	Stop a process by its ID		tech-linux-commands
df -h	Show disk space		tech-linux-commands
du -sh folder	Show a folder's size		tech-linux-commands
free -h	Show memory usage		tech-linux-commands
uname -a	Show system information		tech-linux-commands
date	Show the date and time		tech-linux-commands
ping host	Test network reachability		tech-linux-commands
curl url	Transfer data from a URL		tech-linux-commands
wget url	Download a file		tech-linux-commands
ssh user@host	Log in to a remote machine securely		tech-linux-commands
scp	Copy files securely between machines		tech-linux-commands
tar -czf out.tar.gz folder	Create a compressed archive		tech-linux-commands
tar -xzf file.tar.gz	Extract an archive		tech-linux-commands
zip and unzip	Compress and extract zip files		tech-linux-commands
apt install pkg	Install a package on Debian or Ubuntu		tech-linux-commands
brew install pkg	Install a package on macOS with Homebrew		tech-linux-commands
| (pipe)	Send the output of one command into another		tech-linux-commands
> (redirect)	Write output to a file, replacing it		tech-linux-commands
>> (append)	Add output to the end of a file		tech-linux-commands
< (input redirect)	Use a file as input		tech-linux-commands
&& (and)	Run the next command only if the first succeeds		tech-linux-commands
& (background)	Run a command in the background		tech-linux-commands
* (wildcard)	Matches any characters in filenames		tech-linux-commands
~ (tilde)	Your home directory		tech-linux-commands
. (dot)	The current directory		tech-linux-commands
.. (dot dot)	The parent directory		tech-linux-commands
/ (root)	The top of the file system		tech-linux-commands
Absolute path	A path starting from /		tech-linux-commands
Relative path	A path starting from the current folder		tech-linux-commands
Environment variable	A named value available to programs, like PATH		tech-linux-commands
PATH	A list of folders where the shell looks for commands		tech-linux-commands
export VAR=value	Set an environment variable		tech-linux-commands
Shell	A program that reads your commands		tech-linux-commands
bash	A popular shell		tech-linux-commands
Kernel	The core of an operating system		tech-linux-commands
Linux creator	Linus Torvalds, first released in 1991		tech-linux-commands
Tux	The penguin mascot of Linux		tech-linux-commands
Permissions rwx	Read, write and execute		tech-linux-commands
Hidden file	A file whose name begins with a dot		tech-linux-commands
nano	A simple text editor in the terminal		tech-linux-commands
vim	A powerful text editor, famous for being hard to exit (:q)		tech-linux-commands
Network	Computers and devices connected to share data		tech-networking-terms
LAN	Local area network, such as in a home or school		tech-networking-terms
WAN	Wide area network that spans a large area		tech-networking-terms
Internet	A global network of networks		tech-networking-terms
Intranet	A private network inside an organization		tech-networking-terms
IP address	A number that identifies a device on a network		tech-networking-terms
IPv4 address	Four numbers 0 to 255, like 192.168.1.1		tech-networking-terms
IPv6 address	A longer address format with letters and numbers, made for more devices		tech-networking-terms
Public IP	An address visible on the internet		tech-networking-terms
Private IP	An address used inside a local network, like 192.168.x.x		tech-networking-terms
Localhost (127.0.0.1)	Your own computer		tech-networking-terms
MAC address	A hardware address built into a network card		tech-networking-terms
DNS	Domain Name System, translates names into IP addresses		tech-networking-terms
DHCP	Automatically gives devices IP addresses		tech-networking-terms
NAT	Lets many devices share one public IP address		tech-networking-terms
Router	Forwards data between networks		tech-networking-terms
Switch	Connects devices within a network		tech-networking-terms
Hub	A simple device that repeats data to all ports		tech-networking-terms
Modem	Connects a home to the internet provider		tech-networking-terms
Access point	Gives wireless devices a connection to a network		tech-networking-terms
Gateway	A node that connects one network to another		tech-networking-terms
Firewall	Controls which traffic is allowed in or out		tech-networking-terms
Proxy server	A server that acts as middleman for requests		tech-networking-terms
VPN	Virtual private network that sends traffic through an encrypted tunnel		tech-networking-terms
Protocol	A set of rules for communication		tech-networking-terms
TCP	Reliable, ordered delivery of data		tech-networking-terms
UDP	Fast delivery without guarantees, used in streaming and games		tech-networking-terms
IP (Internet Protocol)	Addresses and routes packets		tech-networking-terms
HTTP	Protocol for web pages		tech-networking-terms
HTTPS	HTTP with encryption		tech-networking-terms
FTP	Protocol for transferring files		tech-networking-terms
SMTP	Protocol for sending email		tech-networking-terms
IMAP and POP3	Protocols for receiving email		tech-networking-terms
SSH	Secure remote login		tech-networking-terms
TLS/SSL	Encryption protocols for secure connections		tech-networking-terms
Port	A numbered door on a device for a type of traffic		tech-networking-terms
Port 80	HTTP		tech-networking-terms
Port 443	HTTPS		tech-networking-terms
Port 22	SSH		tech-networking-terms
Port 25	SMTP email		tech-networking-terms
Port 53	DNS		tech-networking-terms
Packet	A small chunk of data sent over a network		tech-networking-terms
Header	Information at the start of a packet like source and destination		tech-networking-terms
Latency	Delay before data arrives		tech-networking-terms
Bandwidth	Maximum data rate of a connection		tech-networking-terms
Throughput	The actual data rate achieved		tech-networking-terms
Ping	Test of reachability and round-trip time		tech-networking-terms
Traceroute	Shows the path packets take		tech-networking-terms
Jitter	Variation in delay		tech-networking-terms
Packet loss	Packets that never arrive		tech-networking-terms
Wi-Fi	Wireless local networking		tech-networking-terms
Ethernet	A common wired network standard		tech-networking-terms
Fiber optic	Cables that send data as pulses of light		tech-networking-terms
Cellular (4G, 5G)	Mobile phone networks		tech-networking-terms
Bluetooth	Short-range wireless		tech-networking-terms
Subnet	A smaller part of a network		tech-networking-terms
Subnet mask	Tells which part of an address is the network		tech-networking-terms
CIDR notation	Writing a network like 192.168.0.0/24		tech-networking-terms
Client	A device that requests services		tech-networking-terms
Server	A device that provides services		tech-networking-terms
Peer-to-peer	Devices share directly without a central server		tech-networking-terms
Cloud	Computing services offered over the internet		tech-networking-terms
CDN	Content delivery network, servers around the world that make sites load faster		tech-networking-terms
URL	A web address		tech-networking-terms
Domain registrar	A company that sells domain names		tech-networking-terms
ICANN	The organization that coordinates domain names and IP addresses		tech-networking-terms
Web server	Software that serves web pages		tech-networking-terms
API	Rules for programs to talk to each other		tech-networking-terms
REST	A common style for web APIs		tech-networking-terms
Status code 200	OK		tech-networking-terms
Status code 404	Not found		tech-networking-terms
Status code 500	Server error		tech-networking-terms
Status code 301	Moved permanently		tech-networking-terms
OSI model	A seven-layer model of networking		tech-networking-terms
OSI layers	Physical, Data Link, Network, Transport, Session, Presentation, Application		tech-networking-terms
TCP/IP model	A four-layer model that the internet uses		tech-networking-terms
Three-way handshake	SYN, SYN-ACK, ACK to start a TCP connection		tech-networking-terms
Vint Cerf and Bob Kahn	Designed TCP/IP in the 1970s		tech-networking-terms
Print text to the screen	print('Hello')		tech-python-syntax
Get input from the user	input('Name? ')		tech-python-syntax
Make a variable	x = 5		tech-python-syntax
Comment a line	# this is a comment		tech-python-syntax
Integer division	7 // 2 gives 3		tech-python-syntax
Remainder (modulo)	7 % 2 gives 1		tech-python-syntax
Exponent (power)	2 ** 3 gives 8		tech-python-syntax
Not equal comparison	x != y		tech-python-syntax
Equal comparison	x == y		tech-python-syntax
Logical and	a and b		tech-python-syntax
Logical or	a or b		tech-python-syntax
Logical not	not a		tech-python-syntax
If statement	if x > 3:		tech-python-syntax
Else if	elif x == 3:		tech-python-syntax
Else	else:		tech-python-syntax
For loop over a range of 5	for i in range(5):		tech-python-syntax
Range from 1 to 10	range(1, 11)		tech-python-syntax
While loop	while x < 10:		tech-python-syntax
Stop a loop early	break		tech-python-syntax
Skip to the next loop pass	continue		tech-python-syntax
Do nothing placeholder	pass		tech-python-syntax
Define a function	def greet(name):		tech-python-syntax
Return a value	return x		tech-python-syntax
Default parameter	def f(x=10):		tech-python-syntax
Lambda (small anonymous function)	lambda x: x * 2		tech-python-syntax
Make a list	nums = [1, 2, 3]		tech-python-syntax
Add to the end of a list	nums.append(4)		tech-python-syntax
Remove last item of a list	nums.pop()		tech-python-syntax
Length of a list or string	len(nums)		tech-python-syntax
First item of a list	nums[0]		tech-python-syntax
Last item of a list	nums[-1]		tech-python-syntax
Slice the first two items	nums[:2]		tech-python-syntax
Sort a list in place	nums.sort()		tech-python-syntax
Sorted copy of a list	sorted(nums)		tech-python-syntax
Reverse a list	nums.reverse() or nums[::-1]		tech-python-syntax
Tuple (unchangeable sequence)	t = (1, 2, 3)		tech-python-syntax
Set (unique items)	s = {1, 2, 3}		tech-python-syntax
Dictionary	d = {'a': 1, 'b': 2}		tech-python-syntax
Get a dictionary value	d['a']		tech-python-syntax
Loop over dictionary items	for k, v in d.items():		tech-python-syntax
Check if item is in a list	3 in nums		tech-python-syntax
Convert to integer	int('5')		tech-python-syntax
Convert to string	str(5)		tech-python-syntax
Convert to float	float('3.5')		tech-python-syntax
Convert to list	list('abc')		tech-python-syntax
Type of a value	type(x)		tech-python-syntax
Join strings in a list	', '.join(words)		tech-python-syntax
Split a string into a list	'a b c'.split()		tech-python-syntax
Uppercase a string	'hi'.upper()		tech-python-syntax
Replace text in a string	s.replace('a', 'b')		tech-python-syntax
Strip whitespace	s.strip()		tech-python-syntax
F-string	f'Hello {name}'		tech-python-syntax
Multi-line string	'''text over lines'''		tech-python-syntax
Import a module	import math		tech-python-syntax
Import one name	from math import sqrt		tech-python-syntax
Random integer	import random; random.randint(1, 6)		tech-python-syntax
Square root	math.sqrt(16)		tech-python-syntax
Absolute value	abs(-3)		tech-python-syntax
Round a number	round(3.6)		tech-python-syntax
Maximum of values	max(1, 5, 3)		tech-python-syntax
Sum of a list	sum(nums)		tech-python-syntax
List comprehension	[x * 2 for x in nums]		tech-python-syntax
Open and read a file	with open('f.txt') as f: data = f.read()		tech-python-syntax
Handle errors	try: ... except ValueError: ...		tech-python-syntax
Raise an error	raise ValueError('bad')		tech-python-syntax
Define a class	class Dog:		tech-python-syntax
Constructor method	def __init__(self, name):		tech-python-syntax
The current object inside a method	self		tech-python-syntax
None value	None		tech-python-syntax
Boolean values	True and False		tech-python-syntax
Enumerate with index	for i, x in enumerate(nums):		tech-python-syntax
Zip two lists	zip(a, b)		tech-python-syntax
Check if a value is None	x is None		tech-python-syntax
Run code only when file is the main program	if __name__ == '__main__':		tech-python-syntax
Python's creator	Guido van Rossum, who released Python in 1991		tech-python-syntax
Cell	One box in a spreadsheet where a row and column meet		tech-spreadsheet-functions
Cell reference	The cell's address, like B3		tech-spreadsheet-functions
Row	A horizontal line of cells, labeled with numbers		tech-spreadsheet-functions
Column	A vertical line of cells, labeled with letters		tech-spreadsheet-functions
Range	A group of cells, like A1:A10		tech-spreadsheet-functions
Worksheet (sheet)	A single page of cells in a workbook		tech-spreadsheet-functions
Workbook	A file holding one or more sheets		tech-spreadsheet-functions
Formula	A calculation that starts with an equals sign		tech-spreadsheet-functions
Function	A built-in formula like SUM		tech-spreadsheet-functions
=A1+B1	Adds two cells		tech-spreadsheet-functions
=A1*B1	Multiplies two cells		tech-spreadsheet-functions
=SUM(A1:A10)	Adds a range		tech-spreadsheet-functions
=AVERAGE(A1:A10)	Finds the mean of a range		tech-spreadsheet-functions
=MIN(A1:A10)	Finds the smallest value		tech-spreadsheet-functions
=MAX(A1:A10)	Finds the largest value		tech-spreadsheet-functions
=COUNT(A1:A10)	Counts cells with numbers		tech-spreadsheet-functions
=COUNTA(A1:A10)	Counts non-empty cells		tech-spreadsheet-functions
=ROUND(A1,2)	Rounds to two decimal places		tech-spreadsheet-functions
=IF(A1>10,'Yes','No')	Returns one value if true and another if false		tech-spreadsheet-functions
=AND() and =OR()	Test several conditions		tech-spreadsheet-functions
=COUNTIF(range,criteria)	Counts cells that meet a rule		tech-spreadsheet-functions
=SUMIF(range,criteria,sum_range)	Adds cells that meet a rule		tech-spreadsheet-functions
=VLOOKUP()	Looks up a value in the first column of a table		tech-spreadsheet-functions
=XLOOKUP()	A modern lookup function		tech-spreadsheet-functions
=INDEX() and =MATCH()	A flexible way to look things up		tech-spreadsheet-functions
=CONCATENATE() or =A1&B1	Joins text		tech-spreadsheet-functions
=LEFT(A1,3)	Takes the first 3 characters		tech-spreadsheet-functions
=LEN(A1)	Counts characters in a cell		tech-spreadsheet-functions
=UPPER(A1)	Makes text uppercase		tech-spreadsheet-functions
=TODAY()	Shows today's date		tech-spreadsheet-functions
=NOW()	Shows the date and time		tech-spreadsheet-functions
Absolute reference	Locks a cell with dollar signs, like $A$1		tech-spreadsheet-functions
Relative reference	A reference that changes when copied		tech-spreadsheet-functions
Fill handle	The small square in the corner of a cell you drag to copy		tech-spreadsheet-functions
AutoSum	A button that adds a column or row quickly		tech-spreadsheet-functions
Sort	Arrange rows in order		tech-spreadsheet-functions
Filter	Show only rows that meet a condition		tech-spreadsheet-functions
Conditional formatting	Changing cell colors based on values		tech-spreadsheet-functions
Pivot table	A summary table made from many rows of data		tech-spreadsheet-functions
Chart	A visual graph of data		tech-spreadsheet-functions
Bar chart	Compares categories with bars		tech-spreadsheet-functions
Line chart	Shows change over time		tech-spreadsheet-functions
Pie chart	Shows parts of a whole		tech-spreadsheet-functions
Header row	The top row naming each column		tech-spreadsheet-functions
Freeze panes	Keeps the header row visible while scrolling		tech-spreadsheet-functions
Merge cells	Combine cells into one		tech-spreadsheet-functions
Data validation	Limits what can be entered in a cell		tech-spreadsheet-functions
#DIV/0!	Error from dividing by zero		tech-spreadsheet-functions
#REF!	Error from a broken cell reference		tech-spreadsheet-functions
#NAME?	Error from a misspelled function name		tech-spreadsheet-functions
#VALUE!	Error from the wrong type of value		tech-spreadsheet-functions
CSV	A simple text file for spreadsheet data		tech-spreadsheet-functions
Google Sheets	A free online spreadsheet tool		tech-spreadsheet-functions
Microsoft Excel	A popular spreadsheet program first released in 1985		tech-spreadsheet-functions
VisiCalc	The first popular spreadsheet program, from 1979		tech-spreadsheet-functions
Mean	The average, found by adding and dividing		tech-spreadsheet-functions
Median	The middle value when ordered		tech-spreadsheet-functions
Mode	The most common value		tech-spreadsheet-functions
Order of operations	Parentheses, exponents, multiplication and division, then addition and subtraction		tech-spreadsheet-functions
Percent formula	=A1/B1 formatted as a percent		tech-spreadsheet-functions
Number format	Controls how a number looks: currency, date, percent		tech-spreadsheet-functions
Template	A premade spreadsheet layout		tech-spreadsheet-functions
Named range	A name given to a group of cells		tech-spreadsheet-functions
SQL	Structured Query Language, used to work with databases		tech-sql-commands
Database	An organized collection of data		tech-sql-commands
Table	Rows and columns of data in a database		tech-sql-commands
Row (record)	One entry in a table		tech-sql-commands
Column (field)	One attribute shared by all rows		tech-sql-commands
Primary key	A column that uniquely identifies each row		tech-sql-commands
Foreign key	A column linking to the primary key of another table		tech-sql-commands
SELECT	Gets data from a table		tech-sql-commands
SELECT *	Gets every column		tech-sql-commands
FROM	Names the table to read		tech-sql-commands
WHERE	Filters rows by a condition		tech-sql-commands
AND, OR, NOT	Combine or negate conditions		tech-sql-commands
ORDER BY	Sorts the results		tech-sql-commands
ASC / DESC	Sort ascending or descending		tech-sql-commands
LIMIT	Restricts how many rows are returned		tech-sql-commands
DISTINCT	Removes duplicate values from results		tech-sql-commands
LIKE	Matches text patterns		tech-sql-commands
% wildcard	Matches any number of characters in LIKE		tech-sql-commands
_ wildcard	Matches exactly one character in LIKE		tech-sql-commands
IN	Matches any value in a list		tech-sql-commands
BETWEEN	Matches a range of values		tech-sql-commands
IS NULL	Tests for missing values		tech-sql-commands
AS (alias)	Gives a column or table a temporary name		tech-sql-commands
INSERT INTO	Adds new rows to a table		tech-sql-commands
VALUES	Gives the values for an insert		tech-sql-commands
UPDATE	Changes data in existing rows		tech-sql-commands
SET	Names the columns to change in an update		tech-sql-commands
DELETE FROM	Removes rows		tech-sql-commands
CREATE TABLE	Makes a new table		tech-sql-commands
ALTER TABLE	Changes a table's structure		tech-sql-commands
DROP TABLE	Deletes a table entirely		tech-sql-commands
CREATE INDEX	Makes a table lookup faster		tech-sql-commands
COUNT()	Counts rows		tech-sql-commands
SUM()	Adds up values		tech-sql-commands
AVG()	Finds the average		tech-sql-commands
MIN()	Finds the smallest value		tech-sql-commands
MAX()	Finds the largest value		tech-sql-commands
GROUP BY	Groups rows to use with aggregate functions		tech-sql-commands
HAVING	Filters groups after grouping		tech-sql-commands
JOIN	Combines rows from two tables		tech-sql-commands
INNER JOIN	Keeps only rows that match in both tables		tech-sql-commands
LEFT JOIN	Keeps all rows from the left table and matches from the right		tech-sql-commands
RIGHT JOIN	Keeps all rows from the right table and matches from the left		tech-sql-commands
FULL OUTER JOIN	Keeps all rows from both tables		tech-sql-commands
CROSS JOIN	Pairs every row of one table with every row of another		tech-sql-commands
UNION	Combines results of two queries, removing duplicates		tech-sql-commands
UNION ALL	Combines results and keeps duplicates		tech-sql-commands
Subquery	A query inside another query		tech-sql-commands
EXISTS	Tests whether a subquery returns rows		tech-sql-commands
CASE WHEN	Conditional logic inside a query		tech-sql-commands
NULL	A missing or unknown value		tech-sql-commands
NOT NULL	A column must always have a value		tech-sql-commands
UNIQUE	All values in a column must be different		tech-sql-commands
DEFAULT	A value used when none is given		tech-sql-commands
CHECK	A rule that values must satisfy		tech-sql-commands
Transaction	A group of operations that succeed or fail together		tech-sql-commands
COMMIT	Saves a transaction		tech-sql-commands
ROLLBACK	Undoes a transaction		tech-sql-commands
View	A saved query that acts like a table		tech-sql-commands
Index	A structure that speeds up searches		tech-sql-commands
Normalization	Organizing tables to reduce repeated data		tech-sql-commands
Schema	The structure of a database		tech-sql-commands
Relational database	A database storing data in related tables		tech-sql-commands
One-to-many relationship	One row in a table relates to many rows in another		tech-sql-commands
Many-to-many relationship	Many rows relate to many, using a join table		tech-sql-commands
ACID	Atomicity, Consistency, Isolation, Durability, properties of reliable transactions		tech-sql-commands
SQL injection	An attack that sneaks harmful SQL into input; prevent with parameterized queries		tech-sql-commands
Parameterized query	A query with placeholders for safe user input		tech-sql-commands
MySQL, PostgreSQL, SQLite	Popular SQL database systems		tech-sql-commands
NoSQL	Databases that don't use traditional tables, like document stores		tech-sql-commands
Query	A request for data		tech-sql-commands
CRUD	Create, Read, Update, Delete		tech-sql-commands
Front end	What the user sees and interacts with in the browser		tech-web-development-concepts
Back end	The server side that stores data and runs logic		tech-web-development-concepts
Full stack	Working on both front end and back end		tech-web-development-concepts
HTML	Structure and content of a web page		tech-web-development-concepts
CSS	Style and layout of a web page		tech-web-development-concepts
JavaScript	Programming language that makes pages interactive		tech-web-development-concepts
DOM	Document Object Model, the tree of elements in a page that scripts can change		tech-web-development-concepts
Browser dev tools	Built-in tools to inspect and debug pages		tech-web-development-concepts
Responsive design	Pages that adjust to screen size		tech-web-development-concepts
Mobile first	Designing for phones before larger screens		tech-web-development-concepts
Accessibility (a11y)	Making sites usable by people with disabilities		tech-web-development-concepts
Alt text	Text describing an image for screen readers		tech-web-development-concepts
Screen reader	Software that reads page content aloud		tech-web-development-concepts
Semantic HTML	Using tags that describe the meaning of content		tech-web-development-concepts
WCAG	Web Content Accessibility Guidelines		tech-web-development-concepts
SEO	Search engine optimization, helping pages be found in search		tech-web-development-concepts
Meta description	A short page summary shown in search results		tech-web-development-concepts
Domain name	The address people type to visit a site		tech-web-development-concepts
Hosting	A service that stores and serves your website		tech-web-development-concepts
Web server	Software that sends pages to browsers		tech-web-development-concepts
HTTP request	A browser asking a server for something		tech-web-development-concepts
HTTP response	The server's reply		tech-web-development-concepts
GET request	Asks to read data		tech-web-development-concepts
POST request	Sends data to the server		tech-web-development-concepts
Status code	A number telling how a request went		tech-web-development-concepts
Cookie	A small piece of data stored in the browser		tech-web-development-concepts
Local storage	Browser storage for data kept on the user's device		tech-web-development-concepts
Session	A visit during which a server remembers a user		tech-web-development-concepts
API	A way for programs to exchange data		tech-web-development-concepts
REST API	An API style using URLs and HTTP methods		tech-web-development-concepts
JSON	A text format for structured data		tech-web-development-concepts
AJAX / fetch	Loading data without reloading the page		tech-web-development-concepts
Framework	A toolkit for building apps, such as React or Django		tech-web-development-concepts
React	A JavaScript library for building user interfaces		tech-web-development-concepts
Vue and Angular	Other popular front-end frameworks		tech-web-development-concepts
Node.js	Runs JavaScript on servers		tech-web-development-concepts
npm	The package manager for JavaScript		tech-web-development-concepts
Package manager	A tool that installs and updates code libraries		tech-web-development-concepts
Bundler	A tool that combines many files into a few for the browser		tech-web-development-concepts
Minify	Remove spaces and comments to make files smaller		tech-web-development-concepts
Compile / transpile	Convert code into another form		tech-web-development-concepts
TypeScript	JavaScript with types		tech-web-development-concepts
CSS preprocessor	A tool like Sass that extends CSS		tech-web-development-concepts
Database	Where a site stores its data		tech-web-development-concepts
CMS	Content management system, like WordPress		tech-web-development-concepts
Static site	Pages that are fixed files, not made on request		tech-web-development-concepts
Dynamic site	Pages built on request, using data		tech-web-development-concepts
Single-page app (SPA)	A site that loads once and updates without full reloads		tech-web-development-concepts
Server-side rendering	Building pages on the server before sending them		tech-web-development-concepts
Client-side rendering	Building pages in the browser		tech-web-development-concepts
Cache	Stored copies to speed up loading		tech-web-development-concepts
CDN	Network of servers that deliver content quickly worldwide		tech-web-development-concepts
Page load speed	How fast a page appears; faster is better		tech-web-development-concepts
Lazy loading	Loading images only when needed		tech-web-development-concepts
Image optimization	Making images smaller without losing quality		tech-web-development-concepts
HTTPS	Encrypted connection for safety		tech-web-development-concepts
CORS	Rules about which sites can request data from others		tech-web-development-concepts
Authentication	Proving who a user is		tech-web-development-concepts
Authorization	Deciding what a user may do		tech-web-development-concepts
Hash passwords	Never store plain passwords		tech-web-development-concepts
Sanitize input	Clean user input to prevent attacks		tech-web-development-concepts
Deployment	Putting a site online for users		tech-web-development-concepts
Staging	A test version of a site before it goes live		tech-web-development-concepts
Production	The live version of a site		tech-web-development-concepts
Version control	Tracking code changes with Git		tech-web-development-concepts
CI/CD	Automated testing and deployment		tech-web-development-concepts
Unit test	A test of one small piece of code		tech-web-development-concepts
Linting	Automatically checking code for mistakes and style		tech-web-development-concepts
Open source	Code anyone can view and improve		tech-web-development-concepts
Wireframe	A simple sketch of a page layout		tech-web-development-concepts
UX	User experience, how it feels to use something		tech-web-development-concepts
UI	User interface, what the user sees and touches		tech-web-development-concepts
Favicon	The small icon shown in the browser tab		tech-web-development-concepts
Viewport	The visible part of a web page		tech-web-development-concepts