Int 15H [AT] [PS/2] Function 80H (128) Device open

Acquires ownership of a logical device for a process.

Call with:

AH = 80H

BX = device ID

CX = process ID

Returns:

If function successful

Carry flag = clear

AH = 00H

If function unsuccessful

Carry flag = set

AH = status

Note:

This function call, along with Int 15H Functions 81H and 82H, defines a simple protocol that can be used to arbitrate usage of devices by multiple processes. A multitasking program manager would be expected to capture Int 15H and provide the appropriate service. The default BIOS routine for this function simply returns with the carry flag clear and AH = 00H.