The thinking bits of a computer use “flip-flops” to show “up” or “down” or “ on” or “off”. It’s just as easy to think of these as on/off light bulbs. Arrays of these flip-flops are used for storing and manipulating numbers. The point is that they can only have two states like a light bulb. These two states can also be stores as N/S magnets on a hard disk, or pits in foil on CD, or high and low voltages in a cable etc. etc.
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Computers similarly use groups of switches to represent numbers and perform calculations. These groups of switches are known as registers and show numbers in Binary form. Denary numbers (which we also call Decimal) use 10 symbols to represent numbers – 0123456789, whereas Binary needs just two symbols 01.
The number of digits in a binary number can be represented by a corresponding number of switches. In computer parlance, these are bits.
A bit is either a 1 or a 0. The different bits in a binary number represent different values which are used to create a number.
If the bit is switched on (1) then we use that bit. If the bit is switched off (0) then we ignore it. Add all the (1) switches together, 128+64+16+8+1, and you get the number 217. So the binary number for 217 is 11011001.
Binary Number Examples