c07-01.asm

[org 0x0100]

mov  ax, 0xb800         ; video memory base
mov  es, ax             ; cannot move to es through IMM
mov  di, 0              ; top left location 

nextpos: 
    mov  word [es:di], 0x0776       ; 0x07 -- full white  (try 41)
                                    ; 0x20 is the space character
    add  di, 2
    cmp  di, 4000
    jne  nextpos

    mov  ax, 0x4c00
    int  0x21