; File: arrayinc.asm
;
; A subroutine to be called from C programs.
; Parameters: int A[], int n
; Result: A[0], ... A[n-1] are each incremented by 1


        SECTION .text
        global arrayinc

arrayinc:
        push    ebp                     ; set up stack frame
        mov     ebp, esp

        ; registers ebx, esi and edi must be saved, if used
        push    ebx
        push    edi

        mov     edi, [ebp+8]            ; get address of A
        mov     ecx, [ebp+12]           ; get num of elts
        mov     ebx, 0                  ; initialize count 

for_loop:
        mov     eax, [edi+4*ebx]        ; get array element
        inc     eax                     ; add 1
        mov     [edi+4*ebx], eax        ; put it back
        inc     ebx                     ; update counter
        loop    for_loop

        pop     edi                     ; restore registers
        pop     ebx
        
        mov     esp, ebp                ; take down stack frame
        pop     ebp

        ret
        
        
        
        
        linux3% gcc -c arraytest.c
linux3% nasm -f elf arrayinc.asm
linux3% gcc arraytest.o arrayinc.o
linux3% 
linux3% a.out
sizeof(int) = 4

Original array:
A[0] = 2  A[1] = 7  A[2] = 19  A[3] = 45  A[4] = 3  A[5] = 42  A[6] = 9  

Modified array:
A[0] = 3  A[1] = 8  A[2] = 20  A[3] = 46  A[4] = 4  A[5] = 43  A[6] = 10  
linux3% 



// File: arraytest.c
//
// C program to test arrayinc.asm
//

void arrayinc(int A[], int n) ;

main() {

int A[7] = {2, 7, 19, 45, 3, 42, 9} ;
int i ;

   printf ("sizeof(int) = %d\n", sizeof(int)) ;

   printf("\nOriginal array:\n") ;
   for (i = 0 ; i < 7 ; i++) {
      printf("A[%d] = %d  ", i, A[i]) ;
   }
   printf("\n") ;

   arrayinc(A,7) ;

   printf("\nModified array:\n") ;
   for (i = 0 ; i < 7 ; i++) {
      printf("A[%d] = %d  ", i, A[i]) ;
   }
   printf("\n") ;
	
}