This function returns a value specifying whether the EGA.SYS device driver is present.
Input
AH =
Output
AX:
Example
The following example interrogates the driver and displays the results:
gotmsg db "EGA.SYS driver found", 0dh, 0ah, 24h
nopmsg db "EGA.SYS driver not found", 0dh, 0ah, 24h
revmsg db "revision $"
crlf db 0dh, 0ah, 24h
ten db 10
mov bx, 0 ; must be 0 for this call
mov ah, 0fah ; fa = interrogate driver
int 10h ; interrogate!
or bx, bx ; bx = 0 ?
jnz found ; branch if driver present
mov dx, offset nopmsg ; assume nopmsg in data segment
mov ah, 09h ; 9 = print string
int 21h ; output not found message
jmp continue ; that's all for now
found: mov dx, offset gotmsg ; assume gotmsg in data segment
mov ah, 09h ; 9 = print string
int 21h ; output found message
mov dx, offset revmsg ; assume revmsg in data segment
mov ah, 09h ; 9 = print string
int 21h ; output "revision "
mov dl, es:[bx] ; dl = major release number
add dl, "0" ; convert to ASCII
mov ah, 2 ; 2 = display character
int 21h ; output major release number
mov dl, "." ; dl = "."
mov ah, 2 ; 2 = display character
int 21h ; output a period
mov al, es:[bx+1] ; al = minor release number
xor ah, ah ; ah = 0
idiv ten ; al = 10ths, ah = 100ths
mov bx, ax ; save ax in bx
mov dl, al ; dl = 10ths
add dl, "0" ; convert to ASCII
mov ah, 2 ; 2 = display character
int 21h ; output minor release 10ths
mov dl, bh ; dl = 100ths
add dl, "0" ; convert to ASCII
mov ah, 2 ; 2 = display character
int 21h ; output minor release 100ths
mov dx, offset crlf ; assume crlf in data segment
mov ah, 09h ; 9 = print string
int 21h ; output end of line
continue: ; the end