1; 50 lines text mode PCOPY substitute for QBasic.
2push bp           ; Save previous bp.
3mov bp,sp         ; Set new bp.
4push ds           ; Save ds.
5push es           ; Save es.
6push di           ; Save di.
7push si           ; Save si.
8
9mov cx,0xb800     ; Set bx to the first screen page's segment address.
10mov dx,0xba04     ; Set cx to the second screen page's segment address.
11mov bx,[bp+6]     ; Load parameter. (0 = copy, 1 = restore)
12cmp word [bx],0   ; Unless parameter is zero, these addresses are swapped before copying.
13je SkipSwap       ;
14 xchg cx,dx       ;
15SkipSwap:         ;
16
17mov ds,cx         ; Load source segment address.
18mov es,dx         ; Load target segment address.
19xor di,di         ; Set di to zero.
20xor si,si         ; Set si to zero.
21mov cx,4000       ; Set the number of words to be copied.
22rep movsw         ; Copy the source screen page to the target page.
23
24pop si            ; Restore si.
25pop di            ; Restore di.
26pop es            ; Restore es.
27pop ds            ; Restore ds.
28pop bp            ; Restore bp.
29retf 2            ; Return and remove arguments from stack.

1DEFINT A-Z
2CLS
3WIDTH 80, 50
4
5 OPEN "PCOPY50" FOR INPUT LOCK READ WRITE AS 1
6 CLOSE 1
7
8 OPEN "PCOPY50" FOR BINARY LOCK READ WRITE AS 1
9  PCOPY50$ = INPUT$(LOF(1), 1)
10 CLOSE 1
11
12 PRINT STRING$(4000, "*");
13
14 SLEEP 1
15 DEF SEG = VARSEG(PCOPY50$)
16 CALL ABSOLUTE(0, SADD(PCOPY50$))
17
18 CLS
19 SLEEP 1
20 DEF SEG = VARSEG(PCOPY50$)
21 CALL ABSOLUTE(1, SADD(PCOPY50$))
22END