mov bx, Drive ;0 = default, 1 = A, 2 = B, etc.
mov ch, 08h ;device category (must be 08h)
mov cl, 68h ;Sense Media Type
mov dx, seg Media
mov ds, dx
mov dx, offset Media ;ds:dx points to buffer for media type
mov ax, 440Dh ;IOCTL for Block Device
int 21h
jc error_handler ;carry set means error
Sense Media Type (Function 440Dh Minor Code 68h) returns the media type for the specified block device.
Drive
Specifies the drive for which parameters are requested (0 = default drive, 1 = A, 2 = B, etc.).
Media
Points to a 2-byte buffer that receives information on the media type for the given drive. The buffer has the following form:
| Offset | Description |
| 00h | Receives a value specifying whether the media type is the default value. This byte is set to 01h for the default media type and to 00h for any other media type. |
| 01h | Receives a value specifying the media type. This byte is set to 02h for 720K disks, 07h for 1.44-MB disks, and 09h for 2.88-MB disks. |
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 |
This function may also return a device-dependent error value as specified by the device driver.
Sense Media Type returns 0005h (ERROR_ACCESS_DENIED) if the media type for the specified drive cannot be determined or the given drive is not ready. Programs can use Get Extended Error (Function 59h) to retrieve additional information about the error.