.model small
.stack 100h
.data 

screenArr db 2000 dup (0)

.code
.486

start:
    MOV ax,@DATA
    MOV ds,ax

    MOV cx, 40
    MOV bx, OFFSET screenArr

    ; MOV byte ptr [bx], 00h
    ; INC bx
    ; MOV byte ptr [bx], 00h

lp:
    MOV byte ptr [bx], 0
    inc bx
LOOP lp

; input:
;     MOV dx,1900h
;     INT 10h

;     MOV ah,07h
;     INT 21h

exit:
    MOV ax,4C00h
    INT 21h
END start