Bits: how computers store information — Technology, 7–10 years
A computer can keep pictures, words and sounds by using tiny choices between two states: usually 0 and 1.
Two tiny choices
Inside a computer, information is made from bits. Each bit is like a tiny switch that can be in one of two states, written as 0 or 1. Long rows of bits can describe letters, colours, music and much more.
Why only 0 and 1?
Electronic parts can reliably tell whether a signal is present or absent, like a lamp that is on or off. Using two clear states makes storage and copying dependable, even when tiny changes happen inside the machine.
A code for A
Suppose a simple code gives A the number 65. First, write 65 as 64 + 1. Next, mark the 64 place and the 1 place: 1, 0, 0, 0, 0, 0, 1. The computer stores A as 1000001 in this example.
A bit is not a whole word
It is tempting to think that one 0 or 1 must mean one letter, because we read one character at a time. A single bit has only two choices, so several bits must work together to represent a letter, colour or sound.
Files and storage
Photos on a tablet, songs on a phone and saved game positions all become patterns of bits inside storage. More detailed files usually need more bits, which is why a long video takes more space than a short note.
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