_ _  |  |  _ _



 _ ______________


Get Verify State (Function 54H)

 Call:

 AH = 54H

 Return:

 AL
  0 = No verify after write
  1 = Verify after write



Comments:

Function 54H checks whether MS-DOS verifies write operations to disk
files. The status returns in AL: 0 if verify is off, 1 if verify is on.

You can set the verify status with Function 2EH (Set/Reset Verify Flag).

Macro Definition:


get_verify macro
  mov ah,54H
  int 21H
  endm


Example:

The following program displays the verify status:

message db "Verify ","$"
on db "on.",0DH,0AH,"$"
off db "off.",0DH,0AH,"$"
;
begin: display message ;See Function 09H
 get_verify ;THIS FUNCTION
 cmp al,0 ;Is flag off?

  1

_ _  |  |  _ _




_ _  |  |  _ _



_ ______________

 jg ver_on ;No, it's on
 display off ;See Function 09H
 jmp return ;Go home
ver_on: display on ;See Function 09H



2

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_ _  |  |  _ _



 _ ______________


Change Directory Entry (Function 56H)

 Call:

 AH = 56H
 DS:DX
  Pointer to pathname
 ES:DI
  Pointer to second pathname

 Return:

 Carry set:
 AX
  2 = File not found
  3 = Path not found
  5 = Access denied
  17 = Not same device
 Carry not set:
  No error


Comments:

Function 56H renames a file by changing its directory entry. DX must
contain the offset (from the segment address in DS) of an ASCIZ string that
contains the pathname of the entry to be changed. DI must contain the
offset (from the segment address in ES) of an ASCIZ string that contains a
second pathname to which the first is to be changed.

If a directory entry for the first pathname exists, it is changed to the
second pathname.

The directory paths need not be the same; in effect, you can move the file
to another directory by renaming it. You cannot use this function request
to copy a file to another drive, however; if the second pathname specifies a
drive, the first pathname must specify or default to the same drive.

You cannot use this function request to rename an open file, a hidden file,
a system file, or a subdirectory, because it may corrupt your disk.

If there is an error, the carry flag (CF) is set and the error code returns in
AX.

Code
 Meaning
_ ________________________________________________________________

2 One of files is invalid or not open



  3

_ _  |  |  _ _




_ _  |  |  _ _



_ ______________

3 One of paths is invalid or not open

5 First pathname specifies a directory, second pathname specifies an
 existing file; or second directory entry could not be opened

17 Both files not on the same drive


Macro Definition:


rename_file macro old_path,new_path
  mov dx,offset old_path
  push ds
  pop es
  mov di,offset new_path
  mov ah,56H
  int 21H
  endm


Example:

The following program prompts for the name of a file and a new name,
then renames the file.

prompt1 db "Filename: $"
prompt2 db "New name: $"
old_path db 15,?,15 dup (?)
new_path db 15,?,15 dup (?)
crlf db 0DH,0AH,"$"
;
begin: display prompt1 ;See Function 09H
 get_string 15,old_path ;See Function 0AH
 xor bx,bx ;To use BL as index
 mov bl,old_path[1] ;Get string length
 mov old_path[bx+2],0 ;Make an ASCIZ string
 display crlf ;See Function 09H
 display prompt2 ;See Function 09H
 get_string 15,new_path ;See Function 0AH
 xor bx,bx ;To use BL as index
 mov bl,new_path[1] ;Get string length
 mov new_path[bx+2],0 ;Make an ASCIZ string
 display crlf ;See Function 09H
 rename_file old_path[2],new_path[2];THIS FUNCTION
 jc error_rename ;Routine not shown



4

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_ _  |  |  _ _



 _ ______________


Get/Set Date/Time of File(Function 57H)

 Call:

 AH = 57H
 AL = Function code
  0 = Get date and time
  1 = Set date and time
 BX
  Handle
 CX (if AL = 1)
  Time to be set
 DX (if AL = 1)
  Date to be set

 Return:

 Carry set:
 AX
  1 = Invalid function
  6 = Invalid handle
 Carry not set:
 CX (if AL = 0)
  Time file last written
 DX (if AL = 0)
  Date file last written


Comments:

Function 57H gets or sets the time and date when a file was last written.
To get the time and date, AL must contain 0; the time and date return in
CX and DX. To set the time and date, AL must contain 1; CX and DX
must contain the time and date. BX must contain the file handle. The time
and date are in the form described in "Fields of the FCB" in Section 1.9.1.

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

1 AL not 0 or 1

6 Handle in BX invalid or not open



  5

_ _  |  |  _ _




_ _  |  |  _ _



_ ______________


Macro Definition:


get_set_date_time macro handle,action,time,date
   mov bx,handle
   mov al,action
   mov cx,word ptr time
   mov dx,word ptr date
   mov ah,57H
   int 21H
   endm


Example:

The following program gets the date of a file named report.asm in the
current directory on the disk in drive B, increments the day, increments
the month and/or year, if necessary, and sets the new date of the file.

month db 31,28,31,30,31,30,31,31,30,31,30,31
path db "b:report.asm",0
handle dw ?
time db 2 dup (?)
date db 2 dup (?)
;
begin: open_handle path,0 ;See Function 3DH
 mov handle,ax ;Save handle
 get_set_date_time handle,0,time,date ;THIS FUNCTION
 jc error_time ;Routine not shown
 mov word ptr time,cx ;Save time
 mov word ptr date,dx ;Save date
 convert_date date[-24] ;See end of chapter
 inc dh ;Increment day
 xor bx,bx ;To use BL as index
 mov bl,dl ;Get month
 cmp dh,month[bx-1] ;Past last day?
 jle month_ok ;No, go home
 mov dh,1 ;Yes, set day to 1
 inc dl ;Increment month
 cmp dl,12 ;Is it past December?
 jle month_ok ;No, go home
 mov dl,1 ;Yes, set month to 1
 inc cx ;Increment year
month_ok: pack_date date ;See end of chapter
 get_set_date_time handle,1,time,date ;THIS FUNCTION
 jc error_time ;Routine not shown
 close_handle handle ;See Function 3EH
 jc error_close ;Routine not shown



6

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_ _  |  |  _ _



 _ ______________


Get/Set Allocation Strategy (Function 58H)

 Call:

 AH = 58H
 AL
  0 = Get strategy
  1 = Set strategy
 BX (AL = 1)
  0 = First fit
  1 = Best fit
  2 = Last fit

 Return:

 Carry set:
 AX
  1 = Invalid function code
 Carry not set:
 AX (AL = 0)
  0 = First fit
  1 = Best fit
  2 = Last fit


Comments:

Function 58H gets or sets the strategy that MS-DOS uses to allocate
memory when a process requests it. If AL contains 0, the strategy is
returned in AX. If AL contains 1, BX must contain the strategy. The three
possible strategies are:



  7

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_ _  |  |  _ _



_ ______________

Table 0.1

Allocation Strategy

_ _________________________________________________________________________

Value  Name  Description 

_ _________________________________________________________________________

0  First fit   

 MS-DOS starts searching at the lowest available block and
 allocates the first block it finds (the allocated memory is the
 lowest available block). This is the default strategy.

1  Best fit   

 MS-DOS searches each available block and allocates the
 smallest available block that satisfies the request.

2  Last fit   

 MS-DOS starts searching at the highest available block and
 allocates the first block it finds (the allocated memory is the
 highest available block).

_ _________________________________________________________________________

You can use this function request to control how MS-DOS uses its memory
resources.

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

1 AL doesn't contain 0 or 1, or BX doesn't contain 0, 1, or 2.


Macro Definition:


alloc_strat macro code,strategy
  mov bx,strategy
  mov al,code
  mov ah,58H
  int 21H
  endm


Example:

The following program displays the memory-allocation strategy in effect,
then forces subsequent memory allocations to the top of memory by set-
ting the strategy to last fit (code 2).

get equ 0
set equ 1
stdout equ 1
last_fit equ 2
;
first db "First fit ",0DH,0AH
best db "Best fit ",0DH,0AH
last db "Last fit ",0DH,0AH

8

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_ _  |  |  _ _



 _ ______________

;
begin: alloc_strat get ;THIS FUNCTION
 jc alloc_error ;routine not shown
 mov cl,4 ;multiply code by 16
 shl ax,cl ;to calculate offset
 mov dx,offset first ;point to first msg
 add dx,ax ;add to base address
 mov bx,stdout ;handle for write
 mov cs,16 ;write 16 bytes
 mov ah,40h ;write handle
 int 21H ;system call
; jc write_error ;routine not shown
 alloc_strat set,last_fit ;THIS FUNCTION
; jc alloc_error ;routine not shown



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_ _  |  |  _ _



_ ______________


Get Extended Error (Function 59H)

 Call:

 AH = 59H
 BX = 0

 Return:

 AX
  Extended-error code
 BH
  Error class (see text)
 BL
  Suggested action (see text)
 CH
  Locus (see text)

 CL, DX, SI, DI, DS, ES destroyed



Comments:

Function 59H retrieves an extended-error code for the preceding system
call. Each release of MS-DOS extends the error codes to cover new capabil-
ities. These new codes are mapped to a simpler set of error codes based on
MS-DOS Version 2.0, so that existing programs can continue to operate
correctly. Note that this call destroys all registers except CS:IP and
SS:SP.

A user-written Interrupt 24H (Critical-Error Handler Address) can use
Function 59H to get detailed information about the error that caused the
interrupt to be issued.

The input BX is a version indicator that specifies for what level of error
handling the application was written. The current level is 0.

The extended-error code consists of four separate codes in AX, BH, BL,
and CH that give as much detail as possible about the error and suggest
how the issuing program should respond.


10

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_ _  |  |  _ _



 _ ______________


BH\(emError Class

BH returns a code that describes the class of error that occurred:

Class
 Description
_ ________________________________________________________________

1 Out of a resource, such as storage or channels

2 Not an error, but a temporary situation (such as a locked region in
 a file) that is expected to end

3 Authorization problem

4 Internal error in system software

5 Hardware failure

6 System software failure not the fault of the active process (could be
 caused by missing or incorrect configuration files, for example)

7 Application program error

8 File or item not found

9 File or item of invalid format or type, or that is otherwise invalid
 or unsuitable

10 Interlocked file or item

11 Wrong disk in drive, bad spot on disk, or other problem with
 storage medium

12 Other error



  11

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_ _  |  |  _ _



_ ______________


BL\(emSuggested Action

BL returns a code that suggests how the issuing program can respond to
the error:

Action
 Description
_ ________________________________________________________________

1 Retry, then prompt user

2 Retry after a Pause

3 If user entered data such as drive letter or filename, prompt for it
 again

4 Terminate with cleanup

5 Terminate immediately; system so unhealthy that program should
 exit as soon as possible without taking time to close files and
 update indexes

6 Error is informational

7 Prompt user to perform some action, such as changing disks, then
 retry operation


CH\(emLocus

CH returns a code that provides additional information to help locate the
area involved in the failure. This code is particularly useful for hardware
failures (BH=5).

Locus
 Description
_ ________________________________________________________________

1 Unknown

2 Related to random-access block devices, such as a disk drive

3 Related to Network

4 Related to serial-access character devices, such as a printer

5 Related to random-access memory

Your programs should handle errors by noting the error return from the
original system call and then issuing this system call to get the extended-
error code. If the program does not recognize the extended-error code, it
should respond to the original error code.

This system call is available during Interrupt 24H and may be used to
return network-related errors.


12

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_ _  |  |  _ _



 _ ______________


Macro Definition:


get_error macro
  mov ah, 59H
  int 21H
  endm


Example:

Since this function request provides such detailed information, a general
example is not practical. User programs can interpret the various codes to
determine what sort of messages or prompts should be displayed, what
action to take, and whether to terminate the program if recovery from the
errors isn't possible.


  13

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_ _  |  |  _ _



_ ______________


Create Temporary File (Function 5AH)

 Call:

 AH = 5AH
 CX
  Attribute
 DS:DX
  Pointer to pathname, followed by a
  byte of 0, and then by 13 bytes of memory

 Return:

 Carry set:
 AX
  2 = File not found
  3 = Path not found
  4 = Too many open files
  5 = Access denied
 Carry not set:
 AX
  Handle


Comments:

Function 5AH creates a file with a unique name. DX must contain the
offset (from the segment address in DS) of an ASCIZ string that specifies a
pathname and 13 bytes of memory (to hold the filename). CX must con-
tain the attribute to be assigned to the file, as described in Section 1.5.5,
"File Attributes," earlier in this chapter.

MS-DOS creates a unique filename and appends it to the pathname
pointed to by DS:DX, creates the file and opens it in compatibility mode,
then returns the file handle in AX. A program that needs a temporary file
should use this function request to avoid name conflicts.

When the creating process exits, MS-DOS does not automatically delete a
file created with Function 5AH. When you no longer need the file you
should delete it.

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

2 File is invalid or doesn't exist



14

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_ _  |  |  _ _



 _ ______________

3 Directory pointed to by DS:DX is invalid or doesn't exist

4 Too many open files (no handle available)

5 Access denied


Macro Definition:


create_temp macro pathname,attrib
  mov cx,attrib
  mov dx,offset pathname
  mov ah,5AH
  int 21H
  endm



  15

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_ _  |  |  _ _



_ ______________


Example:

The following program creates a temporary file in the directory named
\wp\docs, copies a file named textfile.asc that is in the current directory
into the temporary file, and then closes both files.

stdout equ 1
;
file db "TEXTFILE.ASC",0
path db "\WP\DOCS",0
temp db 13 dup (0)
open_msg db " opened.",0DH,0AH
crl_msg db " created.",0DH,0AH
rd_msg db " read into buffer.",0DH,0AH
wr_msg db "Buffer written to "
cl_msg db "Files closed.",0DH,0AH
crlf db 0DH,0AH
handle1 dw ?
handle2 dw ?
buffer db 512 dup (?)
;
begin: open_handle file,0 ;see Function 3DH
 jc open_error ;routine not shown
 mov handle1,ax ;save handle
 write_handle stdout,file,12 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,open_msg,10 ;see Function 40H
 jc write_error ;routine not shown
 create_temp path,0 ;THIS FUNCTION
 jc create_error ;routine not shown
 mov handle2,ax ;save handle
 write_handle stdout,path,8 ;see Function 40H
 jc write_error ;routine not shown
 display_char "
 write_handle stdout,temp,12 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,crl_msg,11 ;See Function 40H
 jc write_error ;routine not shown
 read_handle handle1,buffer,512 ;see Function 3FH
 jc read_error ;routine not shown
 write_handle stdout,file,12 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,rd_msg,20 ;see Function 40H
 jc write_error ;routine not shown
 write_handle handle2,buffer,512 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,wr_msg,18 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,temp,12 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,crlf,2 ;see Function 40H
 jc write_error ;routine not shown
 close_handle handle1 ;see Function 3EH
 jc close_error ;routine not shown
 close_handle handle2 ;see Function 3EH

16

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_ _  |  |  _ _



 _ ______________

 jc close_error ;routine not shown
 write_handle stdout,cl_msg,15 ;see Function 40H
 jc write_error ;routine not shown



  17

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_ _  |  |  _ _



_ ______________


Create New File (Function 5BH)

 Call:

 AH = 5BH
 CX
  Attribute
 DS:DX
  Pointer to pathname

 Return:

 Carry set:
 AX
  2 = File not found
  3 = Path not found
  4 = Too many open files
  5 = Access denied
  80 = File already exists
 Carry not set:
 AX
  Handle


Comments:

Function 5BH creates a new file. DX must contain the offset (from the seg-
ment address in DS) of an ASCIZ string that specifies a pathname. CX con-
tains the attribute to be assigned to the file, as described in Section 1.5.5,
"File Attributes."

If there is no existing file with the same filename, MS-DOS creates the file,
opens it in compatibility mode, and returns the file handle in AX.

This function request fails if the specified file exists, unlike Function 3CH
(Create Handle), which, under the same circumstances, truncates the file
to a length of 0. In a multitasking system, the existence of a file is used as
a semaphore; you can use this system call as a test-and-set semaphore.



18

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_ _  |  |  _ _



 _ ______________

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

2 File is invalid or doesn't exist

3 Directory pointed to by DS:DX is invalid or doesn't exist

4 No free handles are available in the current process, or internal
 system tables are full

5 Access denied

80 File with the same specification pointed to by DS:DX already exists


Macro Definition:


create_new macro pathname,attrib
  mov cx, attrib
  mov dx, offset pathname
  mov ah, 5BH
  int 21H
  endm


Example:

The following program attempts to create a new file named report.asm in
the current directory. If the file already exists, the program displays an
error message and returns to MS-DOS. If the file doesn't exist and there
are no other errors, the program saves the handle and continues process-
ing.

err_msg db "FILE ALREADY EXISTS",0DH,0AH,"$"
path db "report.asm",0
handle dw ?
;
begin: create_new path,0 ;THIS FUNCTION
 jnc continue ;further processing
 cmp ax,80 ;file already exist?
 jne error ;routine not shown
 display err_msg ;see Function 09H
 jmp return ;return to MS-DOS
continue: mov handle,ax ;save handle
;
; (further processing here)



  19

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_ _  |  |  _ _



_ ______________


Lock (Function 5CH, Code 00H)

 Call:

 AH = 5CH
 AL = 00H
 BX
  Handle
 CX:DX
  Offset of region to be locked
 SI:DI
  Length of region to be locked

 Return:

 Carry set:
 AX
  1 = Invalid function code
  6 = Invalid handle
  33 = Lock violation
  36 = Sharing buffer exceeded
 Carry not set:
  No error


Comments:

Function 5CH, Code 00H, denies all access (read or write) by any other
process to the specified region of the file. BX must contain the handle of
the file that contains the region to be locked. CX:DX (a four-byte integer)
must contain the offset in the file of the beginning of the region. SI:DI (a
four-byte integer) must contain the length of the region.

If another process attempts to use (read or write) a locked region, MS-DOS
retries three times; if the retries fail, MS-DOS issues Interrupt 24H for the
requesting process. You can change the number of retries with Function
44H, Code 0BH (IOCtl Retry).

The locked region can be anywhere in the file. For instance, locking
beyond the end of the file is not an error. A region should be locked for
only a brief period, so if it is locked for more than ten seconds you should
consider it to be an error.

Function 45H (Duplicate File Handle) and Function 46H (Force Duplicate
File Handle) duplicate access to any locked region. Passing an open file to
a child process with Function 4BH, Code 00H (Load and Execute Program)
does not duplicate access to locked regions.

_ ________________________________________________________________

20

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_ _  |  |  _ _



 _ ______________

Warning 

 If a program closes a file that contains a locked region or terminates
 with an open file that contains a locked region, the result is undefined.

_ ________________________________________________________________

Programs that might be terminated by Interrupt 23H (CONTROL-C Handler
Address) or Interrupt 24H (Critical-Error-Handler Address) should trap
these interrupts and unlock any locked regions before exiting.

Programs should not rely on being denied access to a locked region. A
program can determine the status of a region (locked or unlocked) by
attempting to lock the region and examining the error code.

If there is an error, the carry flag (CF) is set and the error code is returned
in AX:

Code
 Meaning
_ ________________________________________________________________

1 File sharing must be loaded to use this function request.

6 The handle in BX is not a valid, open handle.

33 All or part of the specified region is already locked.

36 There is no more room for lock entries in the buffer. Refer to the
 share command in the MS-DOS User's Reference for information
 on allocating more lock entries.


Macro Definition:


lock macro handle,start,bytes
 mov bx, handle
 mov cx, word ptr start
 mov dx, word ptr start+2
 mov si, word ptr bytes
 mov di, word ptr bytes+2
 mov al, 0
 mov ah, 5CH
 int 21H
 endm



  21

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_ _  |  |  _ _



_ ______________


Example:

The following program opens a file named finalrpt in "Deny None" mode
and locks two portions of it: the first 128 bytes and bytes 1024 through
5119. After some (unspecified) processing, it unlocks the same portions and
closes the file.

stdout equ 1
;
start1 dd 0
lgth1 dd 128
start2 dd 1023
lgth2 dd 4096
file db "FINALRPT",0
op_msg db " opened.",0DH,0AH
11_msg db "First 128 bytes locked.",0DH,0AH
12_msg db "Bytes 1024-5119 locked.",0DH,0AH
u1_msg db "First 128 bytes unlocked.",0DH,0AH
u2_msg db "Bytes 1024-5119 unlocked.",0DH,0AH
cl_msg db " closed.:,0DH,0AH
handle dw ?
;
begin: open_handle file,01000010b ;see Function 3DH
 jc open_error ;routine not shown
 write_handle stdout,file,8 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,op_msg,10 ;see Function 40H
 jc write_error ;routine not shown
 mov handle,ax ;save handle
 lock handle,start1,lgth1 ;THIS FUNCTION
 jc lock_error ;routine not shown
 write_handle stdout,11_msg,25 ;see Function 40H
 jc write_error ;routine not shown
 lock handle,start2,lgth2 ;THIS FUNCTION
 jc lock_error ;routine not shown
 write_handle stdout,12_msg,25 ;see Function 40H
 jc write_error ;routine not shown
;
; ( Further processing here )
;
 unlock handle,start1,lgth1 ;See Function 5C01H
 jc unlock_error ;routine not shown
 write_handle stdout,ul_msg,27 ;see Function 40H
 jc write_error ;routine not shown
 unlock handle,start2,lgth2 ;See Function 5C01H
 jc unlock_error ;routine not shown
 write_handle stdout,u2_msg,27 ;See Function 40H
 jc write_error ;routine not shown
 close_handle handle ;See Function 3EH
 jc close_error ;routine not shown
 write_handle stdout,file,8 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,cl_msg,10 ;see Function 40H
 jc write_error ;routine not shown


22

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_ _  |  |  _ _



 _ ______________


Unlock (Function 5CH, Code 01H)

 Call:

 AH = 5CH
 AL = 01H
 BX
  Handle
 CX:DX
  Offset of area to be unlocked
 SI:DI
  Length of area to be unlocked

 Return:

 Carry set:
 AX
  1 = Invalid function code
  6 = Invalid handle
  33 = Lock violation
  36 = Sharing buffer exceeded
 Carry not set:
  No error


Comments:

Function 5CH, Code 01H, unlocks a region previously locked by the same
process. BX must contain the handle of the file that contains the region to
be unlocked. CX:DX (a four-byte integer) must contain the offset in the file
of the beginning of the region. SI:DI (a four-byte integer) must contain the
length of the region. The offset and length must be exactly the same as the
offset and length specified in the previous Function 5CH, Code 00H (Lock).

The description of Function 5CH, Code 00H (Lock) describes how to use
locked regions.



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_ _  |  |  _ _



_ ______________

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

1 File sharing must be loaded to use this function request.

6 The handle in BX is not a valid, open handle.

33 The region specified is not identical to one that was previously
 locked by the same process.

36 There is no more room for lock entries in the buffer. Refer to the
 share command in the MS-DOS User's Reference for information
 on allocating more lock entries.

You should issue Function 59H (Get Extended Error) to list the possible
errors returned by this function.

Macro Definition:


unlock macro handle,start,bytes
 mov bx, handle
 mov cx, word ptr start
 mov dx, word ptr start+2
 mov si, word ptr bytes
 mov di, word ptr bytes+2
 mov al, 1
 mov ah, 5CH
 int 21H
 endm


Example:

The following program opens a file named finalrpt in "Deny None" mode
and locks two portions of it: the first 128 bytes and bytes 1024 through
5119. After some (unspecified) processing, it unlocks the same portions and
closes the file.

stdout equ 1
;
start1 dd 0
lgth1 dd 128
start2 dd 1023
lgth2 dd 4096
file db "FINALRPT",0
op_msg db " opened.",0DH,0AH
11_msg db "First 128 bytes locked.",0DH,0AH
12_msg db "Bytes 1024-5119 locked.",0DH,0AH
u1_msg db "First 128 bytes unlocked.",0DH,0AH
u2_msg db "Bytes 1024-5119 unlocked.",0DH,0AH

24

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_ _  |  |  _ _



 _ ______________

cl_msg db " closed.",0DH,0AH
handle dw ?
;
begin: open_handle file,01000010b ;see Function 3DH
 jc open_error ;routine not shown
 write_handle stdout,file,8 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,op_msg,10 ;see Function 40H
 jc write_error ;routine not shown
 mov handle,ax ;save handle
 lock handle,start1,lgth1 ;See Function 5C00H
 jc lock_error ;routine not shown
 write_handle stdout,11_msg,25 ;see Function 40H
 jc write_error ;routine not shown
 lock handle,start2,lgth2 ;See Function 5C00H
 jc lock_error ;routine not shown
 write_handle stdout,12_msg,25 ;see Function 40H
 jc write_error ;routine not shown
;
; ( Further processing here )
;
 unlock handle,start1,lgth1 ;THIS FUNCTION
 jc unlock_error ;routine not shown
 write_handle stdout,u1_msg,27 ;see Function 40H
 jc write_error ;routine not shown
 unlock handle,start2,lgth2 ;THIS FUNCTION
 jc unlock_error ;routine not shown
 write_handle stdout,u2_msg,27 ;see Function 40H
 jc write_error ;routine not shown
 close_handle handle ;See Function 3EH
 jc close_error ;routine not shown
 write_handle stdout,file,8 ;see Function 40H
 jc write_error ;routine not shown
 write_handle stdout,cl_msg,10 ;see Function 40H
 jc write_error ;routine not shown



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_ ______________


Get Machine Name (Function 5EH, Code 00H)

 Call:

 AH = 5EH
 AL = 0
 DS:DX
  Pointer to 16-byte buffer

 Return:

 Carry set:
 AX
  1 = Invalid function code
 Carry not set:
 CX
  Identification number of local
  computer



Comments:

Function 5EH, Code 0, retrieves the net name of the local computer. DX
must contain the offset (to the segment address in DS) of a 16-byte buffer.
Microsoft Networks must be running.

MS-DOS returns the local computer name (a 16-byte ASCIZ string, padded
with blanks) in the buffer pointed to by DS:DX. CX returns the
identification number of the local computer. If the network was never
installed, the CH register returns with zero and the value in the CL regis-
ter is invalid.

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

1 Microsoft Networks must be running to use this function request.



26

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 _ ______________


Macro Definition:


get_machine_name macro buffer
   mov dx,offset buffer
   mov al,0
   mov ah,5EH
   int 21H
   endm


Example:

The following program displays the name of a Microsoft Networks work-
station.

stdout equ 1
;
msg db "Netname: "
mac_name db 16 dup (?),0DH,0AH
;
begin: get_machine_name mac_name ;THIS FUNCTION
 jc name_error ;routine not shown
 write_handle stdout,msg,27 ;see Function 40H
 jc write_error ;routine not shown



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_ ______________


Printer Setup (Function 5EH, Code 02H)

 Call:

 AH = 5EH
 AL = 02H
 BX
  Assign-list index
 CX
  Length of setup string

 DS:SI
  Pointer to setup string

 Return:

 Carry set:
 AX
  1 = Invalid function code
 Carry not set:
  No error


Comments:

Function 5EH, Code 02H, defines a string of control characters that
MS-DOS adds to the beginning of each file sent to the network printer. BX
must contain the index into the assign list that identifies the printer (entry
0 is the first entry). CX must contain the length of the string. SI must con-
tain the offset (to the segment address in DS) of the string itself. Microsoft
Networks must be running.

MS-DOS adds the setup string to the beginning of each file sent to the
printer, which is specified by the assign-list index in BX. This function
request lets each program that shares a printer have its own printer
configuration. You can use Function 5F02H (Get Assign-List Entry) to
determine which entry in the assign list refers to the printer.

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

1 Microsoft Networks must be running to use this function request.



28

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 _ ______________


Macro Definition:


printer_setup macro index,lgth,string
  mov bx, index
  mov cx, lgth
  mov dx, offset string
  mov al, 2
  mov ah, 5EH
  int 21H
  endm


Example:

The following program defines a printer-setup string that consists of the
control character to print expanded type on Epson-compatible printers.
The printer cancels this mode at the first carriage return, so the effect is to
print the first line of each file sent to the network printer as a title in
expanded characters. The setup string is one character. This example
assumes that the printer is the entry number 3 (the fourth entry) in the
assign list. Use Function 5F02H (Get Assign-List Entry) to determine this
value.

setup db 0EH
;
begin: printer_setup 3,1,setup ;THIS FUNCTION
 jc error ;routine not shown



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_ ______________


Get Assign-List Entry (Function 5FH, Code
02H)

 Call:

 AH = 5FH
 AL = 02H
 BX
  Assign-list index
 DS:SI
  Pointer to buffer for local name
 ES:DI
  Pointer to buffer for remote name

 Return:

 Carry set:
 AX
  1 = Invalid function code
  18 = No more files
 Carry not set:
 BL
  3 = Printer
  4 = Drive
 CX
  Stored user value


Comments:

Function 5FH, Code 02H, retrieves the specified entry from the network
list of assignments. BX must contain the assign-list index (entry 0 is the
first entry). SI must contain the offset (to the segment address in DS) of a
16-byte buffer for the local name. DI must contain the offset (to the seg-
ment address in ES) of a 128-byte buffer for the remote name. Microsoft
Networks must be running.

MS-DOS puts the local name in the buffer pointed to by DS:SI and the
remote name in the buffer pointed to by ES:DI. The local name can be a
null ASCIZ string. BL returns 3 if the local device is a printer or 4 if the
local device is a drive. CX returns the stored user value set with Function
5F03H (Make Assign-List Entry). The contents of the assign list can
change between calls.

You can use this function request to retrieve any entry, or to make a copy
of the complete list by stepping through the table. To detect the end of
the assign list, check for error code 18 (no more files), as you would when
stepping through a directory by using Functions 4EH (Find First File) and

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 _ ______________

4FH (Find Next File).

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

1 Microsoft Networks must be running to use this function request.

18 The index passed in BX is greater than the number of entries in the
 assign list.


Macro Definition:


get_list macro index,local,remote
  mov bx, index
  mov si, offset local
  mov di, offset remote
  mov al,2
  mov ah, 5FH
  int 21H
  endm


Example:

The following program displays the assign list on a Microsoft Networks
workstation, showing the local name, remote name, and device type (drive
or printer) for each entry.

stdout equ 1
printer equ 3
;
local_nm db 16 dup (?),2 dup (20h)
remote_nm db 128 dup (?),2 dup (20h)
header db "Local name",8 dup (20h)
 db "Remote name",7 dup (20h)
 db "Device Type"
crlf db 0dh,0ah,0dh,0ah
drive_msg db "drive"
print_msg db "printer"
index dw ?
;
begin: write_handle stdout,header,51 ;see Function 40H
 jc write_error ;routine not shown
 mov index,0 ;assign list index
ck_list: get_list index,local_nm,remote_nm ;THIS FUNCTION
 jnc got_one ;got an entry
error: cmp ax,18 
 je last_one ;yes
 jmp error ;routine not shown
got_one: push bx ;save device type

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_ ______________

 write_handle stdout,local_nm,148 ;see Function 40H
 jc write_error ;routine not shown
 pop bx ;get device type
 cmp bl,printer ;is it a printer?
 je prntr ;yes
 write_handle stdout,drive_msg,5 ;see Function 40H
 jc write_error ;routine not shown
 jmp get_next ;finish message
prntr: write_handle stdout,print_msg,7 ;see Function 40H
 jc write_error ;routine not shown
get_next: write_handle stdout,crlf,2 ;see Function 40H
 jc write_error ;routine not shown
 inc index ;bump index
 jmp ck_list ;get next entry
last_one: write_handle stdout,crlf,4 ;see Function 40H
 jc write_error ;routine not shown
;



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 _ ______________


Make Assign-List Entry (Function 5FH, Code
03H)

 Call:

 AH = 5FH
 AL = 03H
 BL
  3 = Printer
  4 = Drive
 CX
  User value
 DS:SI
  Pointer to name of source device
 ES:DI
  Pointer to name of destination
  device

 Return:

 Carry set:
 AX
  1 = Invalid function code
  5 = Access denied
  3 = Path not found
  8 = Insufficient memory
  (Other errors particular to the
  network may occur.)
 Carry not set:
  No error


Comments:

Function 5FH, Code 03H, redirects a printer or disk drive (source device)
to a network directory (destination device). BL must contain 3 if the
source device is a printer or 4 if it is a disk drive. SI must contain the
offset (to the segment address in DS) of an ASCIZ string that specifies the
name of the printer, or a drive letter followed by a colon, or a null string
(one byte of 00H). DI must contain the offset (to the segment address in
ES) of an ASCIZ string that specifies the name of a network directory. CX
contains a user-specified 16-bit value that MS-DOS maintains. Microsoft
Networks must be running.

The destination string must be an ASCIZ string of the following form:

machine-name pathname 00H password 00H


  33

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_ ______________

where:

Machine-name is the net name of the server that contains the network
directory;

Pathname is the alias of the network directory (not the directory path) to
which the source device is to be redirected;

00H is a null byte; and

Password is the password for access to the network directory. If no pass-
word is specified, both null bytes must immediately follow the pathname.

If BL=3, the source string must be PRN, LPT1, LPT2, or LPT3. This
function buffers and sends all output for the named printer to the remote-
printer spooler named in the destination string.

If BL=4, the source string can be either a drive letter followed by a colon,
or a null string. If the source string contains a valid drive letter and colon,
this call redirects all subsequent drive-letter references to the network
directory named in the destination string. If the source string is a null
string, MS-DOS attempts to grant access to the network directory with
the specified password.

The maximum length of the destination string is 128 bytes. You can
retrieve the value in CX by using Function 5FH, Code 02H (Get Assign-
List Entry).

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code
 Meaning
_ ________________________________________________________________

1 Microsoft Networks must be running to use this function request;
 the value in BX is not 1 to 4, the source string is in the wrong for-
 mat; the destination string is in the wrong format; or the source
 device is already redirected.

3 The network directory path is invalid or doesn't exist.

5 The network directory/password combination is not valid. This
 does not mean that the password itself was invalid; the directory
 might not exist on the server.

8 There is not enough memory for string substitutions.



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 _ ______________


Macro Definition:


redir macro device,value,source,destination
 mov bl, device
 mov cx, value
 mov si, offset source
 mov es, seg destination
 mov di, offset destination
 mov al, 03H
 mov ah, 5FH
 int 21H
 endm



  35

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_ ______________


Example:

The following program redirects two drives and a printer from a worksta-
tion to a server named harold. It assumes the machine name, directory
names, and driver letters shown:

Local drive Netname
or printer on server Password

E: WORD none
F: COMM fred
PRN: PRINTER quick

printer equ 3
drive equ 4
;
local_1 db "e:",0
local_2 db "f:",0
local_3 db "prn",0
remote_1 db "\harold\word",0,0
remote_2 db "\harold\comm",0,"fred",0
remote_3 db "\harold\printer",0,"quick",0
;
begin: redir local_1,remote_1,drive,0 ;THIS FUNCTION
 jc error ;routine not shown
 redir local_2,remote_2,drive,0 ;THIS FUNCTION
 jc error ;routine not shown
 redir local_3,remote_3,printer,0 ;THIS FUNCTION
 jc error ;routine not shown



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 _ ______________


Cancel Assign-List Entry (Function 5FH, Code
04H)

 Call:

 AH = 5FH
 AL = 04H
 DS:SI
  Pointer to name of source device

 Return:

 Carry set:
 AX
  1 = Invalid function code
  15 = Redirection paused on server
  (Other errors particular to the network
  may occur.)
 Carry not set:
  No error



Comments:

Function 5FH, Code 04H, cancels the redirection of a printer or disk drive
(source device) to a network directory (destination device) made with
Function 5FH, Code 03H (Make Assign-List Entry). SI must contain the
offset (to the segment address in DS) of an ASCIZ string that specifies the
name of the printer or drive whose redirection is to be canceled. Microsoft
Networks must be running.

The ASCIZ string pointed to by DS:SI can contain one of three values:

 o The letter of a redirected drive, followed by a colon. Cancels the
 redirection and restores the drive to its physical meaning.

 o The name of a redirected printer (PRN, LPT1, LPT2, LPT3, or
 their machine-specific equivalents). Cancels the redirection and
 restores the printer name to its physical meaning.

 o A string starting with \\ (2 backslashes). Terminates the connec-
 tion between the local machine and the network directory.

If there is an error, the carry flag (CF) is set and the error code returns in
AX:

Code

  37

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_ _  |  |  _ _



_ ______________

 Meaning
_ ________________________________________________________________

1 Microsoft Networks must be running to use this function request;
 or the ASCIZ string names a nonexistent source device.

15 Disk or printer redirection on the network server is paused.


Macro Definition:


cancel_redir macro local
  mov si, offset local
  mov al, 4
  mov ah, 5FH
  int 21H
  endm


Example:

The following program cancels the redirection of drives E and F and the
printer (PRN) of a Microsoft Networks workstation. It assumes that these
local devices were redirected previously.

local_1 db "e:",0
local_2 db "f:",0
local_3 db "prn",0
;
begin: cancel_redir local_1 ;THIS FUNCTION
 jc error ;routine not shown
 cancel_redir local_2 ;THIS FUNCTION
 jc error ;routine not shown
 cancel_redir local_3 ;THIS FUNCTION
 jc error ;routine not shown



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_ _  |  |  _ _



 _ ______________


Get PSP (Function 62H)

 Call:

 AH = 62H

 Return:

 BX
  Segment address of the Program
  Segment Prefix of the current process



Comments:

Function 62H retrieves the segment address of the currently active process
(the start of the Program Segment Prefix). The address returns in BX.

Macro Definition:


get_psp macro
 mov ah, 62H
 int 21H
 endm


Example:

The following program displays the segment address of its Program Seg-
ment Prefix (PSP) in hexadecimal.

msg db "PSP segment address: H",0DH,0AH,"$"
;
begin: get_psp ;THIS FUNCTION
 convert bx,16,msg[21] ;see end of chapter
 display msg ;see Function 09H



  39

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_ _  |  |  _ _



_ ______________


Get Extended Country Information (Function
65H)

 Call:

 AH = 65H
 AL
  Function (minor) code
 BX
  Code page (-1 = active CON device)
 CX
  Amount of data to return
 DX
  Country ID for which information is to be returned
  (-1=default country)
 ES:DI
  Address of country information buffer

 Return:

 1 = Buffer has been filled
 2 = File not found


Comments:

Function 65H retrieves standard country information. This information
includes country ID, code page, date and time format, currency symbol,
separators (for thousands, decimals, data list, date and time) currency for-
mat flags, digits in currency, and case-mapping information.

The function code passed in AL may be one of the following:

Code
 Description
_ ________________________________________________________________

1 Return standard information

2 Return pointer to uppercase table

3 Return pointer to filename uppercase table

4 Return pointer to collating table

5 Reserved (no entry)

6 Return pointer to collating sequence



40

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_ _  |  |  _ _



 _ ______________

MS-DOS 3.3 provides more country-dependent information than previous
versions of MS-DOS. Only the information for the default country is kept
in the kernel. Country-dependent information for all other countries is
contained in the country.sys file. The MS-DOS nlsfunc command is used
to access the country-dependent information in country.sys using this call.
If the country code and code page number do not match, or if either is
invalid, error code 2 is returned to AX. If CX is less than 5, error code 1 is
returned. If the amount of information requested is greater than the value
of CX, only CX bytes are returned and no error is reported.

If AL = 1, the buffer is filled with the following information:

db 1 ; Information ID
dw ? ; Size (<=38)
dw ? ; Country ID
dw ? ; Code page

If AL = 2, the buffer is filled with the following information:

db 2 ; Information ID
dd ? ; Double-word pointer to uppercase table

If AL = 4, the buffer is filled with the following information:

db 4 ; Information ID
dd ? ; Double-word pointer to filename uppercase table

Both of these tables consist of a length field (two bytes) followed by 128
uppercase values for the upper 128 ASCII characters. The following for-
mula is used to compute the address of an uppercase equivalent in the
table:

Address of outchar = inchar - (256-table_len) = table_start

where:

Parameter
 Meaning
_ ________________________________________________________________

inchar Character to be generated

table_len Length of list of uppercase values (two bytes)

table_start Starting address of uppercase table

outchar Uppercase value for inchar

If inchar is greater than or equal to (256 - table_len), there is an uppercase
equivalent in the table; otherwise, there is not.



  41

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_ _  |  |  _ _



_ ______________

If AL = 6, the buffer is filled with the following information:

db 6 ; Information ID
dd ? ; Double-word pointer to collating sequence

The table is 258 bytes long. The first word is the length of the table. The
rest of the table is 256 ASCII values in the appropriate order.


42

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_ _  |  |  _ _



 _ ______________


Get/Set Global Code Page (Function 66H)

 Call:

 AH = 66H
 AL
  Function (minor) code
 BX
  Code page to set (AL = 2)

 Return:

 Carry set:
 AX 
  02 = File not found
  65 = Device not selected
 Carry not set:
  No error



Comments:

Function 66H gets or sets the code page used by the kernel and all devices.
If no other code page has been set, this function gets the default code page
from DX. If another code page is set, this function retrieves the active
code page from BX.

The MS-DOS nlsfunc command and country.sys must be on the system if
this function is to be used to change the global code page.

The function code may be one of the following:

Code
 Description
_ ________________________________________________________________

1 Get code page

2 Set code page

MS-DOS gets the new code page from the country.sys file. Devices must be
prepared for code page switching before a code page can be selected. To
prepare a device, a device driver that supports code page switching must
be installed by using the device command in the config.sys file. The user

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_ _  |  |  _ _



_ ______________

must also use the prepare keyword with the MS-DOS mode command to
prepare the device for code page switching.

The code page selected must be compatible with the country code specified
in the config.sys file. If MS-DOS cannot read country.sys or other specified
country information file, error code 02 is returned to AX.


44

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_ _  |  |  _ _



 _ ______________


Set Handle Count (Function 67H)

 Call:

 AH = 67H
 BX
  Number of allowed handles

 Return:

 Carry set:
 AX
 Carry not set:
  No error 



Comments:

Function 67H increases or decreases the number of files a program can
have open at one time. The maximum number of files handles is 64K. If
less than 20 are specified, the minimum handle number, 20, is assumed. If
this call is used to reduce the number of allowed handles, the new limit
does not take affect until any handles above the new limit are closed.

The user should use Call 4AH (Set Block) to allocate memory for the
extended handle list if BX is greater than 255. The maximum number for
the value of the config.sys command files is 255.


  45

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_ _  |  |  _ _



_ ______________


Commit File (Function 68H)

 Call:

 AH = 68H
 BX
  File handle

 Return:

 Carry set:
 AX = error
 Carry not set
  No error



Comments:

Function 68H flushes all buffered data for a file without closing it. Using
this call is more efficient than using the traditional close-open sequence,
and is more effective for network environments. This call makes sure that
the disk image of a file is current.


46

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_ _  |  |  _ _



 _ ______________

; Macro Definitions for MS-DOS System Call Examples
;
;*******************
; Interrupts
;*******************
; Interrupt 25H
ABS_DISK_READ macro disk,buffer,num_sectors,first_sector
 mov al,disk
 mov bx,offset buffer
 mov cx,num_sectors
 mov dx,first_sector
 int 25H
 popf
 endm
; Interrupt 26H
ABS_DISK_WRITE macro disk,buffer,num_sectors,first_sector
 mov al,disk
 mov bx,offset buffer
 mov cx,num_sectors
 mov dx,first_sector
 int 26H
 popf
 endm
; Interrupt 27H
STAY_RESIDENT macro last_instruc
 mov dx,offset last_instruc
 inc dx
 int 27H
 endm
;
;
;*******************
; Function Requests
;*******************
; Function Request 00H
TERMINATE_PROGRAM macro
 xor ah,ah
 int 21H
 endm
; Function Request 01H
READ_KBD_AND_ECHO macro
 mov ah,01H
 int 21H
 endm
; Function Request 02H
DISPLAY_CHAR macro character
 mov dl,character
 mov ah,02H
 int 21H
 endm
; Function Request 03H
AUX_INPUT macro
 mov ah,03H
 int 21H
 endm
; Function Request 04H

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_ _  |  |  _ _



_ ______________

AUX_OUTPUT macro
 mov ah,04H
 int 21H
 endm
; Function Request 05H
PRINT_CHAR macro character
 mov dl,character
 mov ah,05H
 int 21H
 endm
; Function Request 06H
DIR_CONSOLE_IO macro switch
 mov dl,switch
 mov ah,06H
 int 21H
 endm
; Function Request 07H
DIR_CONSOLE_INPUT macro
 mov ah,07H
 int 21H
 endm
; Function Request 08H
READ_KBD macro
 mov ah,08H
 int 21H
 endm
; Function Request 09H
DISPLAY macro string
 mov dx,offset string
 mov ah,09H
 int 21H
 endm
; Function Request 0AH
GET_STRING macro limit,string
 mov dx,offset string
 mov string,limit
 mov ah,0AH
 int 21H
 endm
; Function Request 0BH
CHECK_KBD_STATUS macro
 mov ah,0BH
 int 21H
 endm
; Function Request 0CH
FLUSH_AND_READ_KBD macro switch
 mov al,switch
 mov ah,0CH
 int 21H
 endm
; Function Request 0DH
RESET_DISK macro
 mov ah,0DH
 int 21H
 endm
; Function Request 0EH

48

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_ _  |  |  _ _



 _ ______________

SELECT_DISK macro disk
 mov dl,disk[-65]
 mov ah,0EH
 int 21H
 endm
; Function Request 0FH
OPEN macro fcb
 mov dx,offset fcb
 mov ah,0FH
 int 21H
 endm
; Function Request 10H
CLOSE macro fcb
 mov dx,offset fcb
 mov ah,10H
 int 21H
 endm
; Function Request 11H
SEARCH_FIRST macro fcb
 mov dx,offset fcb
 mov ah,11H
 int 21H
 endm
; Function Request 12H
SEARCH_NEXT macro fcb
 mov dx,offset fcb
 mov ah,12H
 int 21H
 endm
; Function Request 13H
DELETE macro fcb
 mov dx,offset fcb
 mov ah,13H
 int 21H
 endm
; Function Request 14H
READ_SEQ macro fcb
 mov dx,offset fcb
 mov ah,14H
 int 21H
 endm
; Function Request 15H
WRITE_SEQ macro fcb
 mov dx,offset fcb
 mov ah,15H
 int 21H
 endm
; Function Request 16H
CREATE macro fcb
 mov dx,offset fcb
 mov ah,16H
 int 21H
 endm
; Function Request 17H
RENAME macro fcb,newname
 mov dx,offset fcb

  49

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_ _  |  |  _ _



_ ______________

 mov ah,17H
 int 21H
 endm
; Function Request 19H
CURRENT_DISK macro
 mov ah,19H
 int 21H
 endm
; Function Request 1AH
SET_DTA macro buffer
 mov dx,offset buffer
 mov ah,1AH
 endm
; Function Request 1BH
DEF_DRIVE_DATA macro
 mov ah,1BH
 int 21H
 endm
; Function Request 1CH
DRIVE_DATA macro drive
 mov dl,drive
 mov ah,1CH
 int 21H
 endm
; Function Request 21H
READ_RAN macro fcb
 mov dx,offset fcb
 mov ah,21H
 int 21H
 endm
; Function Request 22H
WRITE_RAN macro fcb
 mov dx,offset fcb
 mov ah,22H
 int 21H
 endm
; Function Request 23H
FILE_SIZE macro fcb
 mov dx,offset fcb
 mov ah,23H
 int 21H
 endm
; Function Request 24H
SET_RELATIVE_RECORD macro fcb
 mov dx,offset fcb
 mov ah,24H
 int 21H
 endm
; Function Request 25H
SET_VECTOR macro interrupt,handler_start
 mov al,interrupt
 mov dx,offset handler_start
 mov ah,25H
 int 21H
 endm
; Function Request 26H

50

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_ _  |  |  _ _



 _ ______________

CREATE_PSP macro seg_addr
 mov dx,offset seg_addr
 mov ah,26H
 int 21H
 endm
; Function Request 27H
RAN_BLOCK_READ macro fcb,count,rec_size
 mov dx,offset fcb
 mov cx,count
 mov word ptr fcb[14],rec_size
 mov ah,27H
 int 21H
 endm
; Function Request 28H
RAN_BLOCK_WRITE macro fcb,count,rec_size
 mov dx,offset fcb
 mov cx,count
 mov word ptr fcb[14],rec_size
 mov ah,28H
 int 21H
 endm
; Function Request 29H
PARSE macro string,fcb
 mov si,offset string
 mov di,offset fcb
 push es
 push ds
 pop es
 mov al,0FH
 mov ah,29H
 int 21H
 pop es
 endm
; Function Request 2AH
GET_DATE macro
 mov ah,2AH
 int 21H
 endm
; Function Request 2BH
SET_DATE macro year,month,day
 mov cx,year
 mov dh,month
 mov dl,day
 mov ah,2BH
 int 21H
 endm
; Function Request 2CH
GET_TIME macro
 mov ah,2CH
 int 21H
 endm
; Function Request 2DH
SET_TIME macro hour,minutes,seconds,hundredths
 mov ch,hour
 mov cl,minutes
 mov dh,seconds

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_ ______________

 mov dl,hundredths
 mov ah,2DH
 int 21H
 endm
; Function Request 2EH
VERIFY macro switch
 mov al,switch
 mov ah,2EH
 int 21H
 endm
; Function Request 2FH
GET_DTA macro
 mov ah,2FH
 int 21H
 endm
; Function Request 30H
GET_VERSION macro
 mov ah,30H
 int 21H
 endm
; Function Request 31H
KEEP_PROCESS macro return_code,last_byte
 mov al,return_code
 mov dx,offset last_byte
 mov cl,4
 shr dx,cl
 inc dx
 mov ah,31H
 int 21H
 endm
; Function Request 33H
CTRL_C_CK macro action,state
 mov al,action
 mov dl,state
 mov ah,33H
 int 21H
 endm
; Function Request 35H
GET_VECTOR macro interrupt
 mov al,interrupt
 mov ah,35H
 int 21H
 endm
; Function Request 36H
GET_DISK_SPACE macro drive
 mov dl,drive
 mov ah,36H
 int 21H
 endm
; Function Request 38H
GET_COUNTRY macro country,buffer
 local gc_01
 mov dx,offset buffer
 mov ax,country
 cmp ax,0FFH
 jl gc_01

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 _ ______________

 mov al,0ffh
 mov bx,country
gc_01: mov ah,38H
 int 21H
 endm
; Function Request 38H
SET_COUNTRY macro country
 local sc_01
 mov dx,0FFFFH
 mov ax,country
 cmp ax,0FFH
 jl sc_01
 mov al,0ffh
 mov bx,country
sc_01: mov ah,38H
 int 21H
 endm
; Function Request 39H
MAKE_DIR macro path
 mov dx,offset path
 mov ah,39H
 int 21H
 endm
; Function Request 3AH
REM_DIR macro path
 mov dx,offset path
 mov ah,3AH
 int 21H
 endm
; Function Request 3BH
CHANGE_DIR macro path
 mov dx,offset path
 mov ah,3BH
 int 21H
 endm
; Function Request 3CH
CREATE_HANDLE macro path,attrib
 mov dx,offset path
 mov cx,attrib
 mov ah,3CH
 int 21H
 endm
; Function Request 3DH
OPEN_HANDLE macro path,access
 mov dx,offset path
 mov al,access
 mov ah,3DH
 int 21H
 endm
; Function Request 3EH
CLOSE_HANDLE macro handle
 mov bx,handle
 mov ah,3EH
 int 21H
 endm
; Function Request 3FH

  53

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_ _  |  |  _ _



_ ______________

READ_HANDLE macro handle,buffer,bytes
 mov bx,handle
 mov dx,offset buffer
 mov cx,bytes
 mov ah,3FH
 int 21H
 endm
; Function Request 40H
WRITE_HANDLE macro handle,buffer,bytes
 mov bx,handle
 mov dx,offset buffer
 mov cx,bytes
 mov ah,40H
 int 21H
 endm
; Function Request 41H
DELETE_ENTRY macro path
 mov dx,offset path
 mov ah,41H
 int 21H
 endm
; Function Request 42H
MOVE_PTR macro handle,high,low,method
 mov bx,handle
 mov cx,high
 mov dx,low
 mov al,method
 mov ah,42H
 int 21H
 endm
; Function Request 43H
CHANGE_MODE macro path,action,attrib
 mov dx,offset path
 mov al,action
 mov cx,attrib
 mov ah,43H
 int 21H
 endm
; Function Request 4400H,01H
IOCTL_DATA macro code,handle
 mov bx,handle
 mov al,code
 mov ah,44H
 int 21H
 endm
; Function Request 4402H,03H
IOCTL_CHAR macro code,handle,buffer
 mov bx,handle
 mov dx,offset buffer
 mov al,code
 mov ah,44H
 int 21H
 endm
; Function Request 4404H,05H
IOCTL_STATUS macro code,drive,buffer
 mov bl,drive

54

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 _ ______________

 mov dx,offset buffer
 mov al,code
 mov ah,44H
 int 21H
 endm
; Function Request 4406H,07H
IOCTL_STATUS macro code,handle
 mov bx,handle
 mov al,code
 mov ah,44H
 int 21H
 endm
; Function Request 4408H
IOCTL_CHANGE macro drive
 mov bl,drive
 mov al,08H
 mov ah,44H
 int 21H
 endm
; Function Request 4409H
IOCTL_RBLOCK macro drive
 mov bl,drive
 mov al,09H
 mov ah,44H
 int 21H
 endm
; Function Request 440AH
IOCTL_RHANDLE macro handle
 mov bx,handle
 mov al,0AH
 mov ah,44H
 int 21H
 endm
; Function Request 440BH
IOCTL_RETRY macro retries,wait
 mov dx,retries
 mov cx,wait
 mov al,0BH
 mov ah,44H
 int 21H
 endm
; Function Request 440CH
GENERIC_IOCTL_HANDLES macro handle,function,category,buffer
 mov ch,05H
 mov cl,function
 mov dx,offset buffer
 mov bx,handle
 mov ah,44H
 mov al,0CH
 int 21H
 endm
; Function Request 440DH
GENERIC_IOCTL_BLOCK macro drive_num,function,category,parm_blk
 mov ch,08H
 mov cl,function
 mov dx,offset parm_blk - 1

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_ _  |  |  _ _



_ ______________

 mov bx,drive_num
 mov ah,44H
 mov al,0DH
 int 21H
 endm
; Function Request 440EH
IOCTL_GET_DRIVE_MAP macro logical_drv
 mov bx,logical_drv
 mov ah,44H
 mov al,0EH
 int 21H
 endm
; Function Request 440FH
IOCTL_SET_DRIVE_MAP macro logical_drv
 mov bx,logical_drv
 mov ah,44H
 mov al,0FH
 int 21H
 endm
; Function Request 45H
XDUP macro handle
 mov bx,handle
 mov ah,45H
 int 21H
 endm
; Function Request 46H
XDUP2 macro handle1,handle2
 mov bx,handle1
 mov cx,handle2
 mov ah,46H
 int 21H
 endm
; Function Request 47H
GET_DIR macro drive,buffer
 mov dl,drive
 mov si,offset buffer
 mov ah,47H
 int 21H
 endm
; Function Request 48H
ALLOCATE_MEMORY macro bytes
 mov bx,bytes
 mov cl,4
 shr bx,cl
 inc bx
 mov ah,48H
 int 21H
 endm
; Function Request 49H
FREE_MEMORY macro seg_addr
 mov ax,seg_addr
 mov es,ax
 mov ah,49H
 int 21H
 endm
; Function Request 4AH

56

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_ _  |  |  _ _



 _ ______________

SET_BLOCK macro last_byte
 mov bx,offset last_byte
 mov cl,4
 shr bx,cl
 add bx,17
 mov ah,4AH
 int 21H
 mov ax,bx
 shl ax,cl
 dec ax
 mov sp,ax
 mov bp,sp
 endm
; Function Request 4B00H
EXEC macro path,command,parms
 mov dx,offset path
 mov bx,offset parms
 mov word ptr parms[02h],offset command
 mov word ptr parms[04h],cs
 mov word ptr parms[06h],5ch
 mov word ptr parms[08h],es
 mov word ptr parms[0ah],6ch
 mov word ptr parms[0ch],es
 mov al,0
 mov ah,4BH
 int 21H
 endm
; Function Request 4B03H
EXEC_OVL macro path,parms,seg_addr
 mov dx,offset path
 mov bx,offset parms
 mov parms,seg_addr
 mov parms[02H],seg_addr
 mov al,3
 mov ah,4BH
 int 21H
 endm
; Function Request 4CH
END_PROCESS macro return_code
 mov al,return_code
 mov ah,4CH
 int 21H
 endm
; Function Request 4DH
RET_CODE macro
 mov ah,4DH
 int 21H
 endm
; Function Request 4EH
FIND_FIRST_FILE macro path,attrib
 mov dx,offset path
 mov cx,attrib
 mov ah,4EH
 int 21H
 endm
; Function Request 4FH

  57

_ _  |  |  _ _




_ _  |  |  _ _



_ ______________

FIND_NEXT_FILE macro
 mov ah,4FH
 int 21H
 endm
; Function Request 54H
GET_VERIFY macro
 mov ah,54H
 int 21H
 endm
; Function Request 56H
RENAME_FILE macro old_path,new_path
 mov dx,offset old_path
 push ds
 pop es
 mov di,offset new_path
 mov ah,56H
 int 21H
 endm
; Function Request 57H
GET_SET_DATE_TIME macro handle,action,time,date
 mov bx,handle
 mov al,action
 mov cx,word ptr time
 mov dx,word ptr date
 mov ah,57H
 int 21H
 endm
; Function Request 58H
ALLOC_STRAT macro code,strategy
 mov bx,strategy
 mov al,code
 mov ah,58H
 int 21H
 endm
; Function Request 59H
GET_ERROR macro
 mov ah,59
 int 21H
 endm
; Function Request 5AH
CREATE_TEMP macro pathname,attrib
 mov cx,attrib
 mov dx,offset pathname
 mov ah,5AH
 int 21H
 endm
; Function Request 5BH
CREATE_NEW macro pathname,attrib
 mov cx,attrib
 mov dx,offset pathname
 mov ah,5BH
 int 21H
 endm
; Function Request 5C00H
LOCK macro handle,start,bytes
 mov bx,handle

58

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_ _  |  |  _ _



 _ ______________

 mov cx,word ptr start
 mov dx,word ptr start+2
 mov si,word ptr bytes
 mov di,word ptr bytes+2
 mov al,0
 mov ah,5CH
 int 21H
 endm
; Function Request 5C01H
UNLOCK macro handle,start,bytes
 mov bx,handle
 mov cx,word ptr start
 mov dx,word ptr start+2
 mov si,word ptr bytes
 mov di,word ptr bytes+2
 mov al,1
 mov ah,5CH
 int 21H
 endm
; Function Request 5E00H
GET_MACHINE_NAME macro buffer
 mov dx,offset buffer
 mov al,0
 mov ah,5EH
 int 21H
 endm
; Function Request 5E02H
PRINTER_SETUP macro index,lgth,string
 mov bx,index
 mov cx,lgth
 mov dx,offset string
 mov al,2
 mov ah,5EH
 int 21H
 endm
; Function Request 5F02H
GET_LIST macro index,local,remote
 mov bx,index
 mov si,offset local
 mov di,offset remote
 mov al,2
 mov ah,5FH
 int 21H
 endm
; Function Request 5F03H
REDIR macro device,value,source,destination
 mov bl,device
 mov cx,value
 mov si,offset source
  mov es,seg destination
 mov di,offset destination
 mov al,03H
 mov ah,5FH
 int 21H
 endm
; Function Request 5F04H

  59

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_ _  |  |  _ _



_ ______________

CANCEL_REDIR macro local
 mov si,offset local
 mov al,4
 mov ah,5FH
 int 21H
 endm
; Function Request 62H
GET_PSP macro
 mov ah,62H
 int 21H
 endm
;
;
;*******************
; General
;*******************
;
DISPLAY_ASCIIZ macro asciiz_string
 local search,found_it
 mov bx,offset asciiz_string

search:
 cmp byte ptr [bx],0
 je found_it
 inc bx
 jmp short search

found_it:
 mov byte ptr [bx],"$"
 display asciiz_string
 mov byte ptr [bx],0
 display_char 0DH
 display_char 0AH
 endm
;
MOVE_STRING macro source,destination,count
 push es
 push ds
 pop es
 assume es:code
 mov si,offset source
 mov di,offset destination
 mov cx,count
 rep movs es:destination,source
 assume es:nothing
 pop es
 endm
;
CONVERT macro value,base,destination
 local table,start
 jmp start
table db "0123456789ABCDEF"

start:
 push ax
 push bx

60

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_ _  |  |  _ _



 _ ______________

 push dx
 mov al,value
 xor ah,ah
 xor bx,bx
 div base
 mov bl,al
 mov al,cs:table[bx]
 mov destination,al
 mov bl,ah
 mov al,cs:table[bx]
 mov destination[1],al
 pop dx
 pop bx
 pop ax
 endm
;
CONVERT_TO_BINARY macro string,number,value
 local ten,start,calc,mult,no_mult
 jmp start
ten db 10

start:
 mov value,0
 xor cx,cx
 mov cl,number
 xor si,si

calc:
 xor ax,ax
 mov al,string[si]
 sub al,48
 cmp cx,2
 jl no_mult
 push cx
 dec cx

mult:
 mul cs:ten
 loop mult
 pop cx

no_mult:
 add value,ax
 inc si
 loop calc
 endm
;
CONVERT_DATE macro dir_entry
 mov dx,word ptr dir_entry[24]
 mov cl,5
 shr dl,cl
 mov dh,dir_entry[24]
 and dh,1FH
 xor cx,cx
 mov cl,dir_entry[25]
 shr cl,1

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_ _  |  |  _ _



_ ______________

 add cx,1980
 endm
;
PACK_DATE macro date
 local set_bit
;
; On entry: DH=day, DL=month, CX=(year-1980)
;
 sub cx,1980
 push cx
 mov date,dh
 mov cl,5
 shl dl,cl
 pop cx
 jnc set_bit
 or cl,80h

set_bit:
 or date,dl
 rol cl,1
 mov date[1],cl
 endm
;



62

_ _  |  |  _ _