GCD.ASM

WRITELINE MACRO VAR
	LEA DX, VAR
	MOV AH, 09
	INT 21H
ENDM

PUTCHAR MACRO VAR
	MOV DL, VAR
	MOV AH, 02
	INT 21H
ENDM

DISPLAY MACRO VAR, L1, L2

	MOV AX, VAR
	MOV BX, 10     ;INITIALIZES DIVISOR
	MOV DX, 0000H    ;CLEARS DX
	MOV CX, 0000H    ;CLEARS CX
    
	;SPLITTING PROCESS STARTS HERE
	L1:  MOV DX, 0000H    ;CLEARS DX DURING JUMP
	DIV BX      ;DIVIDES AX BY BX
	PUSH DX     ;PUSHES DX(REMAINDER) TO STACK
	INC CX      ;INCREMENTS COUNTER TO TRACK THE NUMBER OF DIGITS
	CMP AX, 0     ;CHECKS IF THERE IS STILL SOMETHING IN AX TO DIVIDE
	JNE L1 ;JUMPS IF AX IS NOT ZERO
    
	L2: 
	POP DX      ;POPS FROM STACK TO DX
	ADD DX, 30H     ;CONVERTS TO IT'S ASCII EQUIVALENT
	
	MOV AH, 02H     
	INT 21H      ;CALLS DOS TO DISPLAY CHARACTER
	LOOP L2    ;LOOPS TILL CX EQUALS ZERO

ENDM

.MODEL SMALL

.DATA	
	M DW 56
	N DW 23
	GCD DW ?
	MSG DB 'GCD ($'
	RES DB ') = $'
.CODE
	
	MOV AX, @DATA
	MOV DS, AX

	MOV AX, M
	MOV BX, N

	CALL GCD1
	WRITELINE MSG
	DISPLAY M, L1, L2
	PUTCHAR ','
	PUTCHAR ' '
	DISPLAY N, L3, L4
	WRITELINE RES
	
	DISPLAY GCD, L5, L6

	JMP EOF

	GCD1 PROC
		LOOP1:
		CMP AX, BX
			JE EOP
			JA ABOVE
			JB BELOW

		ABOVE:
			SUB AX, BX
			JMP LOOP1
		BELOW: 
			SUB BX, AX
			JMP LOOP1

		EOP:  MOV GCD, AX
		RET
	GCD1 ENDP

	EOF:
	MOV AH, 4CH
	INT 21H	
END