Base8

Prefixing

Like Base16 there are prefixing conventions to make it clear that a number is written in Base8 rather than Base10. However, there doesn’t seem to be a standardized prefix.

Wikipedia says:

In programming languages, octal literals are typically identified with a variety of prefixes, including the digit 0, the letters o or q, the digit–letter combination 0o, or the symbol & or $. In Motorola convention, octal numbers are prefixed with @, whereas a small (or capital[13]) letter o[13] or q[13] is added as a postfix following the Intel convention.[14][15] In Concurrent DOS, Multiuser DOS and REAL/32 as well as in DOS Plus and DR-DOS various environment variables like $CLS, $ON, $OFF, $HEADER or $FOOTER support an \nnn octal number notation,[16][17][18] and DR-DOS DEBUG utilizes \ to prefix octal numbers as well.

For example, the literal 73 (base 8) might be represented as 073, o73, q73, 0o73, \73, @73, &73, $73 or 73o in various languages.

Newer languages have been abandoning the prefix 0, as decimal numbers are often represented with leading zeroes. The prefix q was introduced to avoid the prefix o being mistaken for a zero, while the prefix 0o was introduced to avoid starting a numerical literal with an alphabetic character (like o or q), since these might cause the literal to be confused with a variable name. The prefix 0o also follows the model set by the prefix 0x used for hexadecimal literals in the C language; it is supported by Haskell,[19] OCaml,[20] Python as of version 3.0,[21] Raku,[22] Ruby,[23] Tcl as of version 9,[24] PHP as of version 8.1,[25] Rust[26] and ECMAScript as of ECMAScript 6[27] (the prefix 0 originally stood for base 8 in JavaScript but could cause confusion,[28] therefore it has been discouraged in ECMAScript 3 and dropped in ECMAScript 5[29]).