# IDIV - Signed Divide

## Description

Divides the (signed) value in the AX, DX:AX, or EDX:EAX (dividend) by the source operand (divisor) and stores the result in the AX (AH:AL),
DX:AX, or EDX:EAX registers. The source operand can be a general-purpose register or a memory location. The action of this instruction depends
on the operand size (dividend/divisor).

## Instruction

| Opcode        | Assembly   | Op/En | Modern Mode | Legacy Mode | Description                                                                 |
|---------------|------------|-------|-------------|-------------|-----------------------------------------------------------------------------|
| F6 /7         | IDIV r/m8  | M     | Valid       | Valid       | Signed divide AX by r/m8, result in: AL=Quotient, AH=Remainder.             |
| REX + F6 /7   | IDIV r/m8* | M     | Valid       | N.E.        | Signed divide AX by r/m8, result in AL=Quotient, AH=Remainder.              |
| F7 /7         | IDIV r/m16 | M     | Valid       | Valid       | Signed divide DX:AX by r/m16, result in AX=Quotient, DX=Remainder.          |
| F7 /7         | IDIV r/m32 | M     | Valid       | Valid       | Signed divide EDX:EAX by r/m32, result in EAX=Quotient, EDX=Remainder.      |
| REX.W + F7 /7 | IDIV r/m64 | M     | Valid       | N.E.        | Signed divide RDX:RAX by r/m64, result in RAX=Quotient, RDX=Remainder.      |

- In 64-bit mode, r/m8 can not be encoded to access the following byte registers if a REX prefix is used: AH, BH, CH, DH.

## Information

Non-integral results are truncated (chopped) towards 0. The remainder is always less than the divisor in magni- tude. Overflow is indicated
with the #DE (divide error) exception rather than with the CF flag.

In 64-bit mode, the instruction’s default operation size is 32 bits. Use of the REX.R prefix permits access to additional registers (R8-R15).
Use of the REX.W prefix promotes operation to 64 bits. In 64-bit mode when REX.W is applied, the instruction divides the signed value in
RDX:RAX by the source operand. RAX contains a 64-bit quotient; RDX contains a 64-bit remainder.