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Basic Disk Operating System (BDOS) Functions
The Get Disk Parameter Block Address function returns the offset and the segment
base of the BIOS resident disk parameter block of the currently selected drive in BX
and ES. This control block can be used for two purposes. First, the disk parameter
values can be extracted for display and/or space computation. Second, transient
programs can dynamically change the values of current disk parameters when the
disk environment changes, if required. Normally, application programs do not
require this facility. (See Chapter 7 for a definition of the BIOS disk parameter
block.)
SET/GET USER CODE
ENTRY
CL: 20H
DL: OFFH (get)
or
User Code
(set)
FUNCTION 32
SET/GET
USER CODE
RETURN
AL: Current User Code
or
(no value)
The Set/Get User Code function performs one of two operations, depending on the
value in register DL when the function is called. It either returns the number of the
currently active user, or it sets a new current user .
• The Get function is performed when register DL is set to OFFH. The
function returns the value of the currently active user (0 - 15) in register AL.
e The Set function is performed when register DL is set to the currently active
user number (0 - 15). The function changes the current user number to the
value in DL (modulo 16). No value is returned.
4-23
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