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an assembly language question

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sagar474

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Where the instruction so the program are stored
code segment?
data segment?

And how the 8086 differentiates the code and data?

Code:
BITS 16

start:
	mov ax, 07C0h		; Set up 4K stack space after this bootloader
	add ax, 288		; (4096 + 512) / 16 bytes per paragraph
	mov ss, ax
	mov sp, 4096

	mov ax, 07C0h		; Set data segment to where we're loaded
	mov ds, ax


	mov si, text_string	; Put string position into SI
	call print_string	; Call our string-printing routine

	jmp $			; Jump here - infinite loop!


	text_string db 'This is my cool new OS!', 0


print_string:			; Routine: output string in SI to screen
	mov ah, 0Eh		; int 10h 'print char' function

.repeat:
	lodsb			; Get character from string
	cmp al, 0
	je .done		; If char is zero, end of string
	int 10h			; Otherwise, print it
	jmp .repeat

.done:
	ret


	times 510-($-$$) db 0	; Pad remainder of boot sector with 0s
	dw 0xAA55		; The standard PC boot signature
 

FvM

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The code is based on implicite assumptions about the code location. Normally assembly directives would be used to clarify these points. You can however see, that a tiny memory model (cs=ds) is assumed. cs has been set before. Generally all code fetches are using cs, data accesses ds (or partly es), unless overridden explicitely.
 

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