What Does # Mean in Assembly?

Question

For example, what would be the difference between, MOVE 8,D2 and MOVE #8,D2? Just wondering what the # represents and what would happen without it.

Possible duplicate: https://stackoverflow.com/questions/6097958/what-does-the-hash-value-associated-with-the-arm-ldr-instruction-mean — Sigma, Sep 29 '18 at 18:27
@Sigma The linked question is on ARM, this one on m68k - How can this be a duplicate? ARM uses # on offsets as well, m68k doesn't. — tofro, Oct 04 '18 at 08:52

score 4 · Answer 1 · answered Oct 03 '18 at 22:08

in 68k assembly, the # sign denotes immediate constants. Everything else is normally considered an address:

move.w #6,d0

will load the constant immediate value 6 into register d0, while

move.w 6,d0

will do something entirely different: It will fetch the word at the constant address 6 into register d0

score 4 · Accepted Answer · answered Apr 29 '19 at 17:34

In GNU AS, if you use the # before anything else on a given line, the line will be ignored (comment). If use # before a value after an instruction, the value will be considered an immediate. If you want to use in-line comments at that point on the same line, you have to use C-style (i.e., /* comment here */) comments. For example:

# Write the palette to CRAM
lea Palette, a0                 /* Move palette address to a0 */
move.w #size_palette_w-1, d0    /* Loop counter = 8 words in palette */

score 1 · Answer 3 · answered Sep 29 '18 at 18:19

1

Means the following is a number instead of a register.

answered Sep 29 '18 at 18:19

Lakshitha Wisumperuma

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Not necessarily, you can also write `move #foo, d2` using a symbol `foo`. – fuz Sep 29 '18 at 18:22

score 1 · Answer 4 · answered Sep 29 '18 at 18:22

1

Normally in ARM and OP's code means an immediate constant but in other assembler types this symbol is different for example # is the same as $ in x86.

answered Sep 29 '18 at 18:22

Sigma

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What Does # Mean in Assembly?

4 Answers4