An unsigned 8-bit int is a byte which will hold 256 distinct values, which represent

the values 0 to 255.

If it was a signed 8-bit int, the same 256 possible bit patterns would be taken

to represent the numbers -128 to +127.

In "Binary coded decimal", there are two separate four-bit numbers in each byte.

The decimal digits 0..9 are represented by a four-bit binary number from 0000 to 1001

in the normal binary number scheme ( the same as hexadecimal ), except that the

four remaining bit patterns ( which in hexadecimal represent the digits A to F ( ten to fifteen ) ),

are not used for anything.

In Binary coded decimal arithmetic, you can do decimal arithmetic.

It is not as efficient in space usage as binary schemes, a single byte can only have the

value 00 to 99 so 99 different numbers instead of 256 different numbers.

But it was used in many early computers and for some other uses like pocket calculators

and spacecraft