Bytes

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What is a byte?

If you've never encountered terms like "8-bit byte" before, they might be confusing. All an 8-bit byte means is "a group of 8 binary digits." Any single series of binary digits that we treat as a single value is called a "byte." The length of the series can technically be whatever you like, but is almost universally agreed to be exactly eight. Hence the 8 in "8-bit byte."

Similarly, a bit is more verbosely termed a binary digit, and it's simply a number written in base 2. In base 2 numerical notation, the decimal (base ten) numbers 0 and 1 are written just as you'd expect (0, and 1, respectively), but the number "two" is written as 10 (pronounced like "1 two and 0 ones"), not 2. As you can see, we must group at least two bits together to represent the number "two," giving us a "2-bit byte." By the same logic, the number "three" is written as 11 in binary because this represents "1 two and 1 ones," which sums to three. We still only need two bits to do this. But continuing this pattern gives us 100 for "four" because this is "1 four, 0 twos, and 0 ones," and now we are forced to group at least three bits one after the other to represent the number we want to express, giving us "3-bit bytes."

Computer manufacturers continued this pattern until they settled on an agreement with software engineers to use 8-bit bytes unless otherwise stated, making it the conventional default for the overwhelming majority of systems we use today. This agreement to use 8-bit bytes made hexadecimal very handy. Each hexadecimal digit, with its sixteen possible values (zero through fifteen), needs four bits to represent it, as shown in the following table:

Hexadecimal number	8's place (fourth bit)	4's place (third bit)	2's place (second bit)	1's place (first bit)	Pronounced
0	0	0	0	0	"0 eights, 0 fours, 0 twos, 0 ones"
1	0	0	0	1
2	0	0	1	0
3	0	0	1	1
4	0	1	0	0
5	0	1	0	1
6	0	1	1	0
7	0	1	1	1
8	1	0	0	0
9	1	0	0	1
A	1	0	1	0
B	1	0	1	1
C	1	1	0	0
D	1	1	0	1
E	1	1	1	0
F	1	1	1	1	"1 eight, 1 four, 1 two, and 1 one"

Four bits of an "8-bit byte" is exactly half, meaning that one 8-bit byte can be represented with exactly two hexadecimal digits. That's why you'll so often see two hexadecimal digits used to represent the numeric value of a single byte.