ASM help

[stealthFIGHTER]

Hi, I have problems with this piece of code:
-----------------------------------------
:
:
MOV ECX, 3 ; EAX=E
CDQ ; ECX=3
IDIV ECX ; EDX=0
IMUL ... ; EAX=4, EDX=2
:
:
-----------------------------------------
I don't know what does the 2nd function (CDQ) do.

Regards

sF

[Bratsher]

Quote:

stealthFIGHTER (03-31-2001 15:32): Hi, I have problems with this piece of code: ----------------------------------------- : : MOV ECX, 3 ; EAX=E CDQ ; ECX=3 IDIV ECX ; EDX=0 IMUL ... ; EAX=4, EDX=2 : : ----------------------------------------- I don't know what does the 2nd function (CDQ) do. Regards sF

CDQ Convert doubleword (in EAX) to quadword (contained in EDX:EAX) always acts on the EDX:EAX registers, so it does not take an operand. The Quad mantains the sign of the integer contained in EAX.

[Fpc]

About CDQ:
If EAX>0x7FFFFFFF, then EDX=0XFFFFFFFF;
If EAX<=0X7FFFFFFF,then EDX=0X0.
That's all.