Print a decimal formatted 8-bit integer in simplified assembly.

printf.asm

; printf(int)
; by Topher6345
; Prints a decimal-formatted, positive 8-bit integer to stdout.

; for Simple 8-bit Assembler Simulator
; http://schweigi.github.io/assembler-simulator/index.html

	JMP start

hello: DB 78            ; int *hello; The number we wish to print;
			; *hello = [val];

start:
	MOV A, [hello]  ; A = *hello; printf() takes register A as input
	CALL printf	; printf(A);
	DB 0		; return 0;

printf: 
	MOV D, 232	  ; D = 232        ; Point to stdout
	CALL printfThree  ; printfThree(A) ; Print N__
	CALL printfTwo    ; printfTwo(A)   ; Print _N_
	CALL printfOne    ; printfOne(A)   ; Print __N
	RET               ; return 0;     

printfThree:
	DIV 100         ; A/100     ; Divide by 100, store result in register A.
	CALL printfA    ; print(A)  ; Print value in register A to stdout.
	RET             ; return 0;

printfTwo:
	MOV A, [hello]	; A = *hello 
	MOV B, [hello]  ; B = *hello
	DIV 100         ; A / 100   ; Divide by 100 and store result in register A.
	MUL 100		; A * 100   ; Multiply by 100 and store result in register A.
	SUB B,A         ; B = B - A ; Subtract value in register A from original value.
	MOV A, B        ; A = B     ; Assign value in register B to register A.
	DIV 10          ; A/10      ; Divide by 10 and store result in register A.
	CALL printfA    ; print(A)  ; Print value in register A to stdout.
	RET             ; return 0;

printfOne:
	MOV A, [hello]	; A = *hello
	MOV B, [hello]	; B = *hello 
	DIV 10          ; A / 10     ; Divide by 10 and store result in register A.
	MUL 10		; A * 10     ; Multiply by 10 and store result in register A.
	SUB B,A 	; B = B - A  ; Subtract A from original value.
	MOV A, B        ; A = B      ; Assign value in register B to registerA.
	CALL printfA	; print(A)   ; Print value in register A to stdout.
	RET             ; return 0;

printfA:
	ADD A, 48       ; A + ASCII Offset ; Apply offset to value in register A. 
	MOV [D], A	; D* = A           ; Put value in register A in memory location.
        INC D           ; D++              ; Increment memory location.		
	RET