;
; *** Listing 5.3 ***
;
; Program to illustrate flipping from bit-mapped graphics mode to
; text mode and back without losing any of the graphics bit-map.
;
; Assembled with TASM 4.0, linked with TLINK 6.10
; Checked by Jim Mischel 11/21/94
;
Stack   segment para stack 'STACK'
        db      512 dup(0)
Stack   ends

GRAPHICS_SEGMENT equ    0a000h  ;mode 10 bit-map segment
TEXT_SEGMENT    equ     0b800h  ;mode 3 bit-map segment
SC_INDEX        equ     3c4h    ;Sequence Controller Index register
MAP_MASK        equ     2       ;index of Map Mask register
GC_INDEX        equ     3ceh    ;Graphics Controller Index register
READ_MAP        equ     4       ;index of Read Map register

Data    segment para common 'DATA'

GStrikeAnyKeyMsg0       label   byte
        db      0dh, 0ah, 'Graphics mode', 0dh, 0ah
        db      'Strike any key to continue...', 0dh, 0ah, '$'

GStrikeAnyKeyMsg1       label   byte
        db      0dh, 0ah, 'Graphics mode again', 0dh, 0ah
        db      'Strike any key to continue...', 0dh, 0ah, '$'

TStrikeAnyKeyMsg        label   byte
        db      0dh, 0ah, 'Text mode', 0dh, 0ah
        db      'Strike any key to continue...', 0dh, 0ah, '$'

Plane2Save      db      2000h dup (?)   ;save area for plane 2 data
                                        ; where font gets loaded
CharAttSave     db      4000 dup (?)    ;save area for memory wiped
                                        ; out by character/attribute
                                        ; data in text mode
Data    ends

Code    segment para public 'CODE'
        assume  cs:Code, ds:Data
Start   proc    near
        mov     ax,10h
        int     10h             ;select video mode 10h (640x350)
;
; Fill the graphics bit-map with a colored pattern.
;
        cld
        mov     ax,GRAPHICS_SEGMENT
        mov     es,ax
        mov     ah,3            ;initial fill pattern
        mov     cx,4            ;four planes to fill
        mov     dx,SC_INDEX
        mov     al,MAP_MASK
        out     dx,al           ;leave the SC Index pointing to the
        inc     dx              ; Map Mask register

FillBitMap:
        mov     al,10h
        shr     al,cl           ;generate map mask for this plane
        out     dx,al           ;set map mask for this plane
        sub     di,di           ;start at offset 0
        mov     al,ah           ;get the fill pattern
        push    cx              ;preserve plane count
        mov     cx,8000h        ;fill 32K words
        rep stosw               ;do fill for this plane
        pop     cx              ;get back plane count
        shl     ah,1
        shl     ah,1
        loop    FillBitMap
;
; Put up "strike any key" message.
;
        mov     ax,Data
        mov     ds,ax
        mov     dx,offset GStrikeAnyKeyMsg0
        mov     ah,9
        int     21h
;
; Wait for a key.
;
        mov     ah,01h
        int     21h
;
; Save the 8K of plane 2 that will be used by the font.
;
        mov     dx,GC_INDEX
        mov     al,READ_MAP
        out     dx,al
        inc     dx
        mov     al,2
        out     dx,al           ;set up to read from plane 2
        mov     ax,Data
        mov     es,ax
        mov     ax,GRAPHICS_SEGMENT
        mov     ds,ax
        sub     si,si
        mov     di,offset Plane2Save
        mov     cx,2000h/2      ;save 8K (length of default font)
        rep movsw
;
; Go to text mode without clearing display memory.
;
        mov     ax,083h
        int     10h
;
; Save the text mode bit-map.
;
        mov     ax,Data
        mov     es,ax
        mov     ax,TEXT_SEGMENT
        mov     ds,ax
        sub     si,si
        mov     di,offset CharAttSave
        mov     cx,4000/2       ;length of one text screen in words
        rep movsw
;
; Fill the text mode screen with dots and put up "strike any key"
; message.
;
        mov     ax,TEXT_SEGMENT
        mov     es,ax
        sub     di,di
        mov     al,'.'          ;fill character
        mov     ah,7            ;fill attribute
        mov     cx,4000/2       ;length of one text screen in words
        rep stosw
        mov     ax,Data
        mov     ds,ax
        mov     dx,offset TStrikeAnyKeyMsg
        mov     ah,9
        int     21h
;
; Wait for a key.
;
        mov     ah,01h
        int     21h
;
; Restore the text mode screen to the state it was in on entering
; text mode.
;
        mov     ax,Data
        mov     ds,ax
        mov     ax,TEXT_SEGMENT
        mov     es,ax
        mov     si,offset CharAttSave
        sub     di,di
        mov     cx,4000/2       ;length of one text screen in words
        rep movsw
;
; Return to mode 10h without clearing display memory.
;
        mov     ax,90h
        int     10h
;
; Restore the portion of plane 2 that was wiped out by the font.
;
        mov     dx,SC_INDEX
        mov     al,MAP_MASK
        out     dx,al
        inc     dx
        mov     al,4
        out     dx,al           ;set up to write to plane 2
        mov     ax,Data
        mov     ds,ax
        mov     ax,GRAPHICS_SEGMENT
        mov     es,ax
        mov     si,offset Plane2Save
        sub     di,di
        mov     cx,2000h/2      ;restore 8K (length of default font)
        rep movsw
;
; Put up "strike any key" message.
;
        mov     ax,Data
        mov     ds,ax
        mov     dx,offset GStrikeAnyKeyMsg1
        mov     ah,9
        int     21h
;
; Wait for a key before returning to text mode and ending.
;
        mov     ah,01h
        int     21h
        mov     ax,03h
        int     10h
        mov     ah,4ch
        int     21h
Start   endp
Code    ends
        end     Start
