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;;; Display the ASCIIZ string at ds:si via BIOS VIDEO call (real mode only)
Write:
lodsb ; load char to al, increment si
or al, al ; see if it's null
jz .DONE ; if so, we're finished
mov ah, 0x0E ; service 0x0E: output one char
mov bh, 0x00 ; display page 0
mov bl, 0x07 ; char text attrib (white on black)
int 0x10 ; invoke bios
jmp Write ; next char
.DONE:
ret
;;; Probe the video system of the machine via BIOS VIDEO calls, populate
;;; the HARDWARE_INFO buffer (real mode only).
PROBE_VIDEO:
;; identify the display type
call DISP_ID
mov [bDisplayType], al
;; determine the font size
call FONT_SIZE
mov [bFontSize], al
ret
;;; Determine the font size (width in pixels) of the current display.
FONT_SIZE:
cmp al, 0x0a
jl .TRY_OLD
mov al, BYTE 16
ret
.TRY_OLD:
cmp al, BYTE 1
jne .TRY_CGA
mov al, BYTE 14
ret
.TRY_CGA:
cmp al, BYTE 2
jne .TRY_VGA
mov al, BYTE 8
ret
.TRY_VGA:
mov ah, 0x11
mov al, 0x30
mov bh, 0
int 0x10
mov al, cl
ret
;;; Determine the video type via BIOS VIDEO call
DISP_ID:
xor ax, ax
mov ah, 0x1a
int 0x10
cmp al, 0x1a
jne .TRY_EGA
mov al, bl
ret
.TRY_EGA:
mov ah, 0x12
mov bx, 0x10
int 0x10
cmp bx, 0x10
je .OLD_BOARDS
cmp bh, 0
je .EGA_COLOR
mov al, 5
ret
.EGA_COLOR:
mov al, 4
ret
.OLD_BOARDS:
int 0x11
and al, 0x30
cmp al, 0x30
jne .CGA
mov al, 1
ret
.CGA:
mov al, 2
ret
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