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Q74496: MS-DOS Device Driver Names Cannot be Used as File Names

Article: Q74496
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:2.x,3.x,4.x,5.x,6.0,6.2,6.21,6.22
Operating System(s): 
Keyword(s): 
Last Modified: 17-DEC-2000

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The information in this article applies to:

- Microsoft MS-DOS operating system versions 2.11, 3.1, 3.2, 3.21, 3.3, 3.3a, 4.0, 4.01, 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
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SUMMARY
=======

Microsoft MS-DOS reserves certain names for system device drivers. If you try to
name a file using one of these names, you will receive the following error
message:

  Write Fault Error Writing Device <FILENAME.EXT>
  Abort, Retry, Ignore, Fail?

The solution is to change the file name.

MORE INFORMATION
================

Below is a list of default device driver names.

  Name    Function
  ----    --------
  CON     Keyboard and display
  PRN     System list device, usually a parallel port
  AUX     Auxiliary device, usually a serial port
  CLOCK$  System real-time clock
  NUL     Bit-bucket device
  A:-Z:   Drive letters
  COM1    First serial communications port
  LPT1    First parallel printer port
  LPT2    Second parallel printer port
  LPT3    Third parallel printer port
  COM2    Second serial communications port
  COM3    Third serial communications port
  COM4    Fourth serial communications port

To identify system device driver names, use one of the following two commands:

- mem /d | more

- debug d 0070:0000

Additional query words: 6.22 2.x 3.x 4.x 5.00 5.00a 6.00 6.20

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Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS321 kbMSDOS400 kbMSDOS320 kbMSDOS330a kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS310 kbMSDOS500 kbMSDOS330 kbMSDOS401 kbMSDOS500a kbMSDOS211
Version           : MS-DOS:2.x,3.x,4.x,5.x,6.0,6.2,6.21,6.22

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