multiplication

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joachim_neu

Joined: 22 Dec 2003
Posts: 139

joachim_neu 27 Mar 2004, 10:01

hello, what is wrong at this:

mul 0x0A

it comes allways:

Error: Invalid operand

whats wrong?

27 Mar 2004, 10:01

decard

Joined: 11 Sep 2003
Posts: 1092
Location: Poland

decard 27 Mar 2004, 10:24

mul can only take register, or memory argument. You should write for example:

Code:

mov ebx,0x0a
mul ebx

Code:

mul [my_variable]

regards

27 Mar 2004, 10:24

joachim_neu

Joined: 22 Dec 2003
Posts: 139

joachim_neu 27 Mar 2004, 10:41

i don't understand... doesn't mul multiplicate the AX register with the given parameter of mul?

27 Mar 2004, 10:41

decard

Joined: 11 Sep 2003
Posts: 1092
Location: Poland

decard 27 Mar 2004, 11:17

yes, it does. It multiplies the accumulator (which is AX or EAX - it depends on your parameter's size) by the given parameter. But this given parameter cannot be just a number (like in your example). It ahs to be some register or memory address. So, in your case (with 16 bit code) you sould try something like:

Code:

mov bx,0x0A
mul bx

and it will multiply AX by BX. BX holds value of 0x0A, so it will calculate AX*0x0A.

27 Mar 2004, 11:17

joachim_neu

Joined: 22 Dec 2003
Posts: 139

joachim_neu 29 Mar 2004, 10:28

oh, so it only multiplicates with a register, ok...

29 Mar 2004, 10:28

aaro

Joined: 21 Jun 2003
Posts: 107
Location: hel.fi

aaro 29 Mar 2004, 10:40

and with memory

29 Mar 2004, 10:40

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