Print_Integer.asm

section .data
        digit db 0
        
section .text
        global _start
        
_start:
        mov rax, 1234                   ; store 1234 in rax, the integer to print
        call _printInteger              ; call subroutine '_printInteger'
        
        ; perform sys_exit
        mov rax, 60
        mov rdi, 0
        syscall

; prints integer in rax
_printInteger:
        mov rcx, digit                  ; start at beginning of integer
        mov rbx, 10                     ; move newline into rbx
        mov [rcx], rbx                  ; move newline into rcx
        inc rcx                         ; increment rcx (position)

; loop to store value of integer
_loopStore:
        xor rdx, rdx                    ; zero-out rdx register
        mov rbx, 10                     ; (divide rbx
        div rbx                         ; by 10)

        add rdx, 48                     ; rdx is the remainder of rax / rbx, and add 48 to give its ASCII value

        mov [rcx], dl                   ; load the character of rdx
        inc rcx                         ; increment position

        cmp rax, 0                      ; (continue loop until
        jne _loopStore                  ; rax becomes 0)

; loop to print string backwards
_loopPrint:
        push rcx                        ; push rcx into stack
        
        ; perform sys_write
        mov rax, 1
        mov rdi, 1
        mov rsi, rcx
        mov rdx, 1
        syscall
        
        pop rcx                        ; get back position
        dec rcx                        ; decrement position
        cmp rcx, digit                 ; (continue loop until 
        jge _loopPrint                 ; end of string)
        ret