Let us look at a computer. It is built from a few parts. Two of them are a CPU and memory. The CPU follows a program, which is a list for a computer. A programmer writes the list. The CPU can add two numbers.

Now let us see how it keeps things. RAM is fast memory. It holds the programs and files a computer is using right now. RAM loses what it holds when the power goes off. Saved files are still there when the power goes off.

Next, let us see how it counts. A bit is the smallest piece of storage. It holds a 0 or a 1. A byte is a group of 8 bits. A byte can store one letter. Each extra bit doubles the number of patterns that bits can make.

Here is a fact about pictures. A picture on a screen is made of many tiny squares called pixels. Inside a computer, a picture is stored with only 0s and 1s. Binary is a number system that uses only 0 and 1.

Now let us go back to 1947. In that year, John Bardeen and Walter Brattain built the first semiconductor amplifier. It was named the transistor. Transistors can also work as switches in computers. One computer chip can hold billions of them.

Words to know

• memory: holding place
• transistor: tiny switch
• pixels: tiny squares
• doubles: two times more