Numeric Notations

Often the question is asked "What is the notation for <octal/hex/binary/base-ten> numbers in software"?

There are sometimes incomplete or conflicting notations. Please add any other forms. Reformatted as a table for easier comparison. -sf

NOTE: not all forms listed below are actually syntactically correct; rather, the forms would be correct if taken to their extremes and actually implemented.

Intel/ 6502/68K Raw Form CeeLanguage Zilog Ada/VHDL assembler RexxLanguage Verilog

Binary 10011101 0b10011101 10011101B 2#10011101 %10011101 '10011101'b 8'b10011101 Octal 5 05 05O 8#5 @5 '101'b 4'o5 Hex 1F 0x1F 01FH 16#1F $1F '1F'x 8'h1F Decimal 27 27 27 27 27 27 27

Footnotes:

In CeeLanguage/CeePlusPlus; any integer literal starting with 0x is hex, anything starting with 0 is octal. Decimal integer literals must start with 1-9; fortunately the number "0" is the same whether decimal or hex. The lexemes for floating point numbers (things with a decimal point in them) are always decimal in C/C++.
'$' has been used as a hex prefix for many years (AppleTwo assembly, many ForthLanguage implementations)

There are conflicts. For instance, is "1001" binary or base-ten? Lexical analysis will not be able to resolve the difference, although a LALR syntax analyzer might - with proper context

Why is there no nice notation for binary. . . or "why doesn't C/C++ recognize 1001B as binary?"

Dunno; it would be useful, especially given the low-level bit-frobbing that C/C++ are frequently used for.
- Binary literals (0b1001010) are added to many embedded C compilers, such as for PIC microcontrollers, since you do a lot bit-level I/O on these devices.

Some languages have an arbitrary-radix format.

Verilog, a hardware description language, extends number to include "don't care's" and "high-impedance" values as well as traditional numbers.

 <length>'<radix><digits>

Where <length> is the number of bits in the value, written decimal, <radix> is the radix expressed as one of h, d, o, or b, and <digits> is the actual number, written in base <radix>. 0-9 are themselves, a-f represent 10 through 15, z represents hi-impedance, x represents "don't care". Some examples are

10'd1023 3'b1zz 3'b101 3'o7 32'hdead_beef

Other languages have similar constructs.

shouldn't the same example value (e.g. 42 2A 52 101010) be used for all bases?

I interpreted the original idea behind this page as demonstrating syntax, not arithmetic equality. In fact, I used the same numbers which were originally posted by the original author. --SamuelFalvo?