NASM and a piece of sample code for those learning

[parksie]

Having started to learn asm this morning, I have now created my first application, and I am posting it here so that others can have a slight head start.

This is for the Netwide Assembler (NASM), a free assembler that produces object code for all x86 platforms. I used NASM, and VAL, an experimental linker.

NASM - http://www.web-sites.co.uk/nasm
VAL (requires LHA to unpack) - ftp://x2ftp.oulu.fi/pub/msdos/progra...ng/00index.txt

I made this using the free syntax-coloured editor NasmEdit, free from http://www.inglenook.co.uk/nasmedit/nasmedit.zip

; Title:	Looped Hello World
;==========================================================================================================;
	segment code			; Begin code segment

..start:	mov ax, data			; Put address of data segment into DS
	mov ds, ax			; No data path from memory to DS, so AX used as temporary storage
	mov ax, stack			; Stack onto SS
	mov ss, ax
	mov sp, stacktop		; Top of stack onto SP (stack pointer)

	mov cl, 0x31			; Initialise CL to '1'

startpt:	mov dx, hello			; Put address of hello into DX
	mov ah, 0x9			; Set AH to 9 (Output string)
	int 0x21			; DOS Interrupt 21

	mov ah, 0x2			; Set AH to 2 (Output character)
	mov dl, cl			; Copy CL to DL
	int 0x21			; DOS Interrupt 21

	mov dx, crlf			; Put address of crlf into DX
	mov ah, 0x9			; Set AH to 9 (Output string)
	int 0x21			; DOS Interrupt 21

	add cl, 0x1			; Add 1 to CL
	cmp cl, 0x36			; Compare CL to '5'
	je end			; If equal, jump to end
	jmp startpt			; Jump back to start

end:	mov ax, 0x4c00		; Set AX to 4c00 (Exit)
	int 0x21			; DOS Interrupt 21
;==========================================================================================================;
	segment data			; Begin data segment

hello:	db 'Hello World from Mike! This is time: ', '$'	; All DOS strings end in a $ sign.
crlf	db 13, 10, '$'
;==========================================================================================================;
	segment stack stack		; Begin stack segment
	resb 32			; Reserve 32 bytes on the stack
stacktop:				; Set top of stack

It was originally in hello.asm

I hope this is of help to anyone.