Function 440Dh Minor Code 41h Write Track on Logical Drive

mov bx, Drive ;0 = default, 1 = A, 2 = B, etc.

mov ch, 08h ;device category (must be 08h)

mov cl, 41h ;Write Track on Logical Drive

mov dx, seg WriteBlock

mov ds, dx

mov dx, offset WriteBlock ;ds:dx points to RWBLOCK structure

mov ax, 440Dh ;IOCTL for Block Device

int 21h

jc error_handler ;carry set means error

Write Track on Logical Drive (Function 440Dh Minor Code 41h) writes data from a buffer to a track on the specified device.

Parameters

Drive

Specifies the drive information is to be written to (0 = default drive, 1 = A, 2 = B, etc.).

WriteBlock

Points to an RWBLOCK structure that contains information that specifies the sectors to be written to. The rwBuffer field must contain the address of the buffer that contains the data to write to the disk. The RWBLOCK structure has the following form:

RWBLOCK STRUC

rwSpecFunc db 0 ;special functions (must be zero)

rwHead dw ? ;head to read/write

rwCylinder dw ? ;cylinder to read/write

rwFirstSector dw ? ;first sector to read/write

rwSectors dw ? ;number of sectors to read/write

rwBuffer dd ? ;address of buffer for read/write data

RWBLOCK ENDS

For a full description of the RWBLOCK structure, see Chapter 3, “File System.”

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
0002h	ERROR_FILE_NOT_FOUND
0005h	ERROR_ACCESS_DENIED

Comment

Write Track on Logical Drive returns 0002h (ERROR_FILE_NOT_FOUND) if the specified drive number is invalid.