; regeax.asm   for regeaxing various things
; Assemble:	nasm -f elf -l regeax.lst  regeax.asm
; Link:		gcc -o regeax  regeax.o
; Run:		regeax
; Output:
; eax=789ABCDE
; eax=789A1234   loading a part of a register, leaves rest same
; eax=789A05DE
; eax=789ABC06

        global main		; the standard gcc entry point
        extern	printf		; the C function, to be called
        section .data		; Data section, initialized variables
a:	dd	5		; int a=5;
fmt:    db "eax=%X",10,0	; The printf format, "\n",'0'


        section .text           ; Code section.
main:				; the program label for the entry point
        push    ebp		; set up stack frame
        mov     ebp,esp
	push	ebx
	
	mov	eax,0x789abcde
	push	eax
        push    dword fmt	; address of ctrl string
        call    printf		; Call C function
        add     esp,8		; pop stack, 2 push times 4 bytes

	mov	eax,0x789abcde
	mov	ax,0x1234	; stuff in lower half
	push	eax
        push    dword fmt	; address of ctrl string
        call    printf		; Call C function
        add     esp,8		; pop stack, 2 push times 4 bytes

	mov	eax,0x789abcde
	mov	ah,5		; stuff byte
	push	eax
        push    dword fmt	; address of ctrl string
        call    printf		; Call C function
        add     esp,8		; pop stack, 2 push times 4 bytes

	mov	eax,0x789abcde
	mov	al,6		; stuff byte
	push	eax
        push    dword fmt	; address of ctrl string
        call    printf		; Call C function
        add     esp,8		; pop stack, 2 push times 4 bytes

	pop	ebx
        mov     esp, ebp	; take down stack frame
        pop     ebp		; same as "leave" op
	mov	eax,0		;  normal, no error, return value
	ret			; return