Hexadecimal: a shorthand for binary
Computer Science · Key Stage 3 · The School
Sixteen digits, not ten or two
HEXADECIMAL uses sixteen digits: 0 to 9, then A, B, C, D, E, F standing for 10 to 15. Binary needs many digits for a large number. Hex packs the same value into far fewer characters, which is exactly why people use it instead of writing out long strings of binary.
Four bits, one hex digit
Binary 1111 is 15, which is hex F. Binary 1010 is 10, which is hex A. Every group of exactly FOUR binary digits maps to exactly ONE hex digit, with nothing left over. That clean match is the whole reason hex was chosen: split any binary number into groups of four, and each group converts on its own.
Converting a full byte
Take the binary number 10110110. Split it into two groups of four: 1011 and 0110. 1011 is 11, which is hex B. 0110 is 6, which is hex 6. So 10110110 in binary is B6 in hex — two short characters instead of eight long ones.
A website colour code like #FF5733 is hex: FF is red, 57 is green, 33 is blue, each a two-digit hex value from 00 to FF. A memory address in a debugger might read 0x7FFE2A1C. Both are binary underneath, made readable by hex. Nobody debugging real code wants to read out a colour as twenty-four 1s and 0s — hex turns something long and easy to mistype into something short enough to actually check by eye.