Octal
Write each character as its code point in base 8.
Octal is base 8, so it counts 0 through 7 and then carries.
It was the natural way to write machine words on computers built around 12, 24
and 36 bit registers, where the bits divide neatly into threes, and it survives
in odd corners such as Unix file permissions.
255 is 377 in octal, so every code is three digits wide and they run together
with nothing between them. A capital A is 101.
The same idea in other bases: binary, decimal and hexadecimal.
Examples: