[org 0x0100]
jmp start
message: db 'MC170202078' ; string to be printed
length: dw 20 ; length of string
clrscr: push es
push ax
push cx
push di
mov ax, 0xb800
mov es, ax ; point es to video base
xor di, di ; point di to top left column
mov ax, 0x0720 ; space char in normal attribute
mov cx, 2000 ; number of screen locations
cld ; auto increment mode
rep stosw ; clear the whole screen
pop di
pop cx
pop ax
pop es
ret
; subroutine to print a string
; takes the x position, y position, attribute, address of string and
; its length as parameters
printstr: push bp
mov bp, sp
push es
push ax
push cx
push si
push di
mov ax, 0xb800
mov es, ax ; point es to video base
mov al, 80 ; load al with columns per row
mul byte [bp+10] ; multiply with y position
add ax, [bp+12] ; add x position
shl ax, 1 ; turn into byte offset
mov di,ax ; point di to required location
mov si, [bp+6] ; point si to string
mov cx, [bp+4] ; load length of string in cx
mov ah, [bp+8] ; load attribute in ah
cld ; auto increment mode
nextchar: lodsb ; load next char in al
stosw ; print char/attribute pair
loop nextchar ; repeat for the whole string
pop di
pop si
pop cx
pop ax
pop es
pop bp
ret 10
start: call clrscr ; call the clrscr subroutine
mov ax, 10
push ax ; push x position
mov ax, 15;
push ax ; push y position
mov ax, 0x12 ; blue on black attribute
push ax ; push attribute
mov ax, message
push ax ; push address of message
push word [length] ; push message length
call printstr ; call the printstr subroutine
mov ax, 0x4c00 ; terminate program
int 0x21

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