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Groups > comp.os.msdos.programmer > #4042

assembly: mov a memory word into register

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I somehow got stuck on a simple quest: copying a word from memory into a
register. Here's what I do:

  void myfunc(char *buff) {
    _asm {
      mov ax, [buff]
    }
  }

This is inline assembly within OpenWatcom. My understanding so far was
that:

  mov ax, buff    ; copies buff (pointer) into AX
  mov ax, [buff]  ; copies *buff (first word at memory location) into AX

But that's not what happens now.

Whether I use "mov ax, buff" or "mov ax, [buff]", the result is the
same: AX gets the address of buff and never the value under it.

What am I missing?

I must add that it works when I do this:

  void myfunc(char *buff) {
    _asm {
      mov bx, buff
      mov ax, [bx]
    }
  }

I'd like to understand why my first version isn't producing what I
expect, though... Any ideas?


Mateusz

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Thread

assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-12 14:35 +0100
  Re: assembly: mov a memory word into register "Kerr-Mudd, John" <admin@127.0.0.1> - 2021-11-12 16:52 +0000
  Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-12 17:53 +0100
    Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-12 18:40 +0100
      Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-12 19:19 +0100
        Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-12 20:07 +0100
          Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-12 22:18 +0100
      Re: assembly: mov a memory word into register rridge@csclub.uwaterloo.ca (Ross Ridge) - 2021-11-15 16:53 +0000
  Re: assembly: mov a memory word into register Rod Pemberton <noemail@basdxcqvbe.com> - 2021-11-14 20:53 -0500
    Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-15 09:31 +0100
      Re: assembly: mov a memory word into register Herbert Kleebauer <klee@unibwm.de> - 2021-11-15 12:10 +0100
        Re: assembly: mov a memory word into register Mateusz Viste <mateusz@xyz.invalid> - 2021-11-15 13:02 +0100

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