MS-DOS Device Driver Names Cannot be Used as File Names (74496)


The information in this article applies to:
    • Microsoft MS-DOS operating system 2.11
    • Microsoft MS-DOS operating system 3.1
    • Microsoft MS-DOS operating system 3.2
    • Microsoft MS-DOS operating system 3.21
    • Microsoft MS-DOS operating system 3.3
    • Microsoft MS-DOS operating system 3.3a
    • Microsoft MS-DOS operating system 4.0
    • Microsoft MS-DOS operating system 4.01
    • Microsoft MS-DOS operating system 5.0
    • Microsoft MS-DOS operating system 5.0a
    • Microsoft MS-DOS operating system 6.0
    • Microsoft MS-DOS operating system 6.2
    • Microsoft MS-DOS operating system 6.21
    • Microsoft MS-DOS operating system 6.22
This article was previously published under Q74496

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
Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB74496
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