; call1.asm  a basic structure for a subroutine to be called from "C"
;
; This saves more registers than used here
; Parameters: int L[] or  int *L
; Result: L[0]=0  L[1]=0

        global call1		; linker must know name of subroutine
call1:				; name must appear as a nasm label
        push	ebp		; save ebp
        mov	ebp, esp	; ebp is callers stack
        push	ebx		; save registers
        push	edi
	push	esi

        mov	edi,[ebp+8]	; get address of L into edi
        mov	eax,0		; get a 32-bit zero 
        mov	[edi],eax	; L[0]=0
        add	edi,4		; add one dword=32-bit int
        mov	[edi],eax	; L[1]=0

        pop	esi		; restore registers
	pop	edi		; in reverse order
        pop	ebx
        mov	esp,ebp		; restore callers stack frame
        pop	ebp
        ret			; return
;
; Notes about the callers stack, ebp in our code:
; ebp+8  is the last argument passed to us by the caller,
;        this is our first argument
; ebp+12 would be our second argument, etc. +4 each
;        the arguments can be values or addresses,
;        as defined by the "C" function prototypes
; ebp+4  is the return address in the caller, used by 'ret'
; ebp    which is our starting esp, is the next available stack space