;; exnl1.asm     example  print string, integer, float
;;;              semicolon, one or more is comment 
; sections contain specific information:
; section .data   is for initialized variables, strings, arrays, etc.
; section .rodata is for initialized constants, protected, not changeable
; section .bss    is block starting symbol for uninitialized arrays, etc.
; section .txt    is last, for program instructions, define macros before use 
;       print using printf (everything same as C)
        extern	printf		; the C function, to be called

        section .data		; Data section, initialized variables
msg:	db "nasm  exnl1.asm running", 0  ; C string needs 0
msg2:	db "exnl1.asm finished", 0	
fmt:    db "%s", 10, 0          ; The printf format, "\n",'0' string format
i:	dq 9999                 ; integer as quad word
fmti:	db "i = %d", 10, 0	; integer format
x:	dq 37.1                 ; floating point as quad word
fmtx:	db "x = %f", 10, 0	; floating point format
        section .text           ; Code section.
        global main		; the standard gcc entry point
main:				; the program label for the entry point
        push    rbp		; set up stack frame, must be aligned

				; print string
	mov	rdi,fmt         ; address of format, required register rdi
	mov	rsi,msg         ; address of data
	mov	rax,0		; or can be  xor  rax,rax
        call    printf		; Call C function
	
				; print integer
	mov	rdi,fmti        ; address of format, required register rdi
	mov	rsi,[i]         ; value of data
	mov	rax,0		; number of float to print
        call    printf		; Call C function
	
				; print float or double
	movq	xmm0, qword[x]	; value of data
	mov	rdi,fmtx        ; address of format, required register rdi
	mov	rax,1		; number of float to print
        call    printf		; Call C function


	mov	rdi,fmt
	mov	rsi,msg2
	mov	rax,0
	call	printf
        pop     rbp		; restore stack 
	mov	rax,0		; normal, no error, return value
	ret			; return