Why 1 byte equals to 8 bits?

Answer 1

Because 1 byte is defined [now] to be 8 bits.

Digital computers use binary memory locations, ie each memory location can hold one of two values: 0 or 1, as each state is easily representable by whether an electrical charge/voltage exists or not.

However, using a BInary digiT, or bit for short, to represent data is not very useful as there are only the two possible data items: 0 and 1. However, by combining more binary digits together into a single unit, more data can be represented in each unit:

Using 1 bit only 2 numbers can be represented: 0 & 1

Using 2 bits, 4 numbers can be represented: 0, 1, 2 & 3

Using 3 bits, 8 numbers can be represented: 0, 1, 2, 3, 4, 5, 6 & 7

Using 4 bits, 16 numbers can be represented: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 & 15

And so on, every additional bit doubling the quantity of numbers that can be represented.

Using 8-bit storage units, two decimal digits can be stored (quite efficiently); this is Binary Coded Decimal (BCD). 8-bit computers became popular (with the manufacturers) probably due to BCD storing two decimal digits in a single unit. I don't know the entymology fully, but I guess that back in the 1950s they needed a term to describe this 8-bit storage unit and either considered it an extended bit (bitE) or as there were eight bits, bit-eight abbreviated to bite. However, it would be very easy to mis- read or write this, so it was deliberately misspelled with a 'y' instead of the 'i': byte.

Early microprocessor digital computers used 4 bit units, so that in one storage unit one of 16 different numbers could be stored: 0-9 (the decimal numbers ) and a further 6 numbers (10-15, often represented by the hexadecimal "digits" A-F).

When wanting a word to describe the 4-bit storage, the term nybble (nibble spelt with a 'y' - to match bite with a 'y') was probably coined as a pun on taking 2 nibbles of something (eg a piece of cake) and getting a bite out of it.