nasm x86-64 bit division

Question

I'm trying to divide in assembly language

I can't find a good example online on how to divide in 64 bit.

So far I have 2 values in two variabbles

input
input2

which where read in

I'm able to multiply fine, but i'm stuck on the division

so if i wan't to divide the two integers, i'm doing

mov rcx, [input]

mov rdi, [input2]

idiv rcx, rdi

that automatically give sme an error, because the division is suppose to be only one register, so i'm assuming that when using idiv, it automatically divides some register, by the one you specify, so i tried

idiv rcx

but i'm getting "floating point error"

ideas?

Your question is tagged [floating-point], but you're talking about integer division. Which is it? — Carl Norum, Jan 13 '12 at 02:48

Carl Norum · Accepted Answer · 2012-01-13T02:48:30.857

4

A quick look in the documentation shows two possibilities for division involving 64-bit numbers:

IDIV r/m32

Signed divide EDX:EAX by r/m32, with result stored in EAX ← Quotient, EDX ← Remainder.

IDIV r/m64

Signed divide RDX:RAX by r/m64, with result stored in RAX ← Quotient, RDX ← Remainder.

It's going to be integer division though. Your question is tagged floating point - if you want floating point division, you'll need one of the variants of the FDIV instruction.

edited Jan 13 '12 at 02:48

answered Jan 13 '12 at 02:42

Carl Norum

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ok....so do i load my integer into rdx and rax, then when i division i do idiv rax? – user1050632 Jan 13 '12 at 02:52
3

No, you do `idiv REGISTER_YOU_WANT_TO_DIVIDE_BY`. Using `RDX` or `RAX` isn't going to work, since that's where your dividend is. – Carl Norum Jan 13 '12 at 03:04

nasm x86-64 bit division

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