Clear Screen with Video Memory [Intel 8086]

.8086
.model small
.stack 2048

;there's no data segment because it's not needed
cseg    segment para public 'code'
assume  cs:cseg

Main  proc
    mov ax,0b800h   ;B800 is the video memory adress
    mov es,ax       ;move that adress to es
                    ;es stands for "extra segment"


    mov bx, ' '     ;space to bx. A space is what we will write in screen (to clean)
    xor di, di      ;di -> 0
    mov cx, 24*80   ;24*80 is the size of window! 24 lines,80 columns

ciclo:
    mov es:[di], bx ;move the space to video adreess (in other words, write a space on screen)
    add di, 2       ;every video adress have a size of word, so let's add 2
    loop ciclo      ;repeat until cx = 0, In every loop, cx is decremented


    mov ah,4CH
    int 21H
main    endp

cseg    ends
end     main