Need help in assembly code with modulus

[slicer]

Hi I am trying to compute the modulus of two numbers in assembly code. As I am more fluent in C++ it is hard for me to understand the concept of modulus as all I use is the symbol % to compute. The problem I am doing is computing the exponent of X to the Y power and then the modulus of this answer with Z. Where X, Y, and Z are one digit numbers input from the keyboard. This is what I have so far.

mov	ah,1
	int	21h          ;input X

	mov	bl,al	;move X to register bl

	mov	ah,1
	int	21h          ;input Y

	mov	cl,al	;move Y to register cl

	mov	ah,1
	int 	21h          ;input Z

	mov	dl,al	;move Z to register dl
	mov	al,bl	;move X back to al for multiplication

loop:			
	mul	al	;multiply X to itself 
	sub	cl,1	;decrement Y
	cmp	cl,1	;compare to see if Y is 1
	jne	loop	;if Y is greater than 1 jump to loop

	mod	al,dl	;???MODULUS??? I know this isn't       
                                                ;right, it is the part i need help with

	mov	dl,al	;move answer to dl

	mov	ah,2	
	int	21h	;ouput answer

[thines01]

If the operand is a byte value, DIV divides the contents of AX by the contents of the operand, then stores the result in AL and the remainder in AH. If the operand is a WORD value, DIV divides the contents of DX:AX by the contents of the operand, then stores the result in AX and the remainder in DX. This instruction treats numbers as unsigned binary values.

WORD EXAMPLE

mov ax, 5h ; number to divide goes in AX
mov bx, 2h ; dividing-by (operand)
div bx     ; perform division. <- WORD division
           ; Stores integer result in AL and remainder in DX
int 20h

;C:\science\asm>debug MODULUS.COM
;-r
;AX=0000  BX=0000  CX=000A  DX=0000  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0100   NV UP EI PL NZ NA PO NC
;14BD:0100 B80500        MOV     AX,0005
;-p
;
;AX=0005  BX=0000  CX=000A  DX=0000  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0103   NV UP EI PL NZ NA PO NC
;14BD:0103 BB0200        MOV     BX,0002
;-p
;
;AX=0005  BX=0002  CX=000A  DX=0000  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0106   NV UP EI PL NZ NA PO NC
;14BD:0106 F7F3          DIV     BX
;-p
;AX=0002  BX=0002  CX=000A  DX=0001  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0108   NV UP EI PL NZ NA PO NC
;14BD:0108 CD20          INT     20
;-p
;
;Program terminated normally
;-q

Byte Example

mov ax, 5h ; number to divide goes in AX
mov bx, 2h ; dividing-by (operand)
div bl     ; perform division. <- BYTE division
           ; Stores integer result in AL and remainder in DX
int 20h

; BYTE Example
;C:\science\asm>debug MODULUS.COM
;-r
;AX=0000  BX=0000  CX=000A  DX=0000  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0100   NV UP EI PL NZ NA PO NC
;14BD:0100 B80500        MOV     AX,0005
;-p
;
;AX=0005  BX=0000  CX=000A  DX=0000  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0103   NV UP EI PL NZ NA PO NC
;14BD:0103 BB0200        MOV     BX,0002
;-p
;
;AX=0005  BX=0002  CX=000A  DX=0000  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0106   NV UP EI PL NZ NA PO NC
;14BD:0106 F6F3          DIV     BL
;-p
;
;AX=0102  BX=0002  CX=000A  DX=0000  SP=FFFE  BP=0000  SI=0000  DI=0000
;DS=14BD  ES=14BD  SS=14BD  CS=14BD  IP=0108   NV UP EI PL NZ NA PO NC
;14BD:0108 CD20          INT     20
;-p
;
;Program terminated normally

[thines01]

...all of that means you get the modulus by calling DIV.
The modulus will be in AH (for BYTE division) or in DX (for WORD division).

[slicer]

Thank you that fixed my problem