Function 440Ch Minor Code 7Fh Get Display Mode

mov bx, Handle ;handle of device

mov ch, 03h ;screen device category

mov cl, 7Fh ;Get Display Mode

mov dx, seg Mode

mov ds, dx

mov dx, offset Mode ;points to buffer for display mode

mov ax, 440Ch ;IOCTL for Character Device

int 21h

jc error_handler ;carry set means error

Get Display Mode (Function 440Ch Minor Code 7Fh) retrieves the display mode for the screen device.

Parameters

Handle

Identifies the device to get the display mode for.

Mode

Points to a DISPLAYMODE structure that receives the display-mode information. Before the function is called, the dmInfoLevel field must be 0 and the dmDataLength field must be 14. The DISPLAYMODE structure has the following form:

DISPLAYMODE STRUC

dmInfoLevel db 0 ;information level (must be zero)

dmReserved1 db ? ;reserved

dmDataLength dw ? ;length of remaining data, in bytes

dmFlags dw ? ;control flags

dmMode db ? ;display mode

dmReserved2 db ? ;reserved

dmColors dw ? ;number of colors

dmWidth dw ? ;screen width, in pixels

dmLength dw ? ;screen length, in pixels

dmColumns dw ? ;columns

dmRows dw ? ;rows

DISPLAYMODE ENDS

For more information about the DISPLAYMODE structure, see Chapter 4, “Character Input and Output.”

Return Value

If the function is successful, the carry flag is clear. Otherwise, the carry flag is set and the AX register contains an error value, which may be one of the following:

Value

Name

0001h	ERROR_INVALID_FUNCTION
0005h	ERROR_ACCESS_DENIED
0006h	ERROR_INVALID_HANDLE

Comments

The function returns 0001h (ERROR_INVALID_FUNCTION) if the ANSI.SYS driver has not been loaded.