Number bases in short
- Binary (base 2) uses 0 and 1, the way computers store everything.
- Octal (base 8) uses 0–7. You’ll see it in Unix file permissions like
755. - Decimal (base 10) is everyday counting.
- Hexadecimal (base 16) uses 0–9 and A–F. It’s used for colours (
#FF5A1F), memory addresses and bytes: two hex digits are exactly one byte.
Example
255 in decimal is 11111111 in binary (eight 1s, one full byte), 377 in octal and FF in hex.