the.com/hexadecimal
counting on sixteen fingers, because computers think in nibbles, not toes.
means a base-16 number system using 0-9 then a-f as extra digits, used to write binary data in a shorter, human-readable form.
from binary is compact for machines but unreadable for humans, and octal (base 8) didn't map cleanly onto 8-bit bytes; base 16 does, since one hex digit equals exactly four bits, so IBM helped popularize it in the 1960s as computing shorthand.
one digitrepresents exactly 4 binary bits, a nibble
ff means255 in decimal, the max byte value
letters useda through f stand in for 10 through 15
prefix 0xsignals hex in most programming languages
for instance
mac addresses — network hardware ids written as six hex pairs
memory addresses — debuggers show ram locations like 0x7ffee
unicode code points — characters like u+1f600 identified in hex