Q46878: Loading File with DOS Device Name (CON) Can Hang QuickBASIC

Article: Q46878
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 13-DEC-1989

Loading or saving files that have the same base name as a DOS device
(e.g. COM1, AUX, CON, PRN, etc.) can cause the QB.EXE editor to hang
for varying lengths of time. This information applies to Microsoft
QuickBASIC Versions 4.00, 4.00b, and 4.50 for MS-DOS.

With the QBX.EXE editor for Microsoft BASIC PDS 7.00, the message
"Operation Requires Disk" is displayed and returns you to the MS-DOS
prompt when you try to load a file with a MS-DOS device name as the
base filename from the QBX.EXE command line. When trying to load or
save files from the File menu, QBX.EXE editor gives the message "File
already exists. Overwrite?" If you answer yes to the prompt, the
message "Path/File access error" is displayed.

To avoid hanging, or error messages, do not use DOS device names as
base names for your files.

For example, trying to load a file in QB.EXE with the base name of
"comX", where "X" is the number of an installed serial port, causes
the QuickBASIC environment to hang for approximately one minute.
Attempting to save a file named "comX" results in a longer delay and a
"Disk full" error message. This occurs regardless of the extension of
the base filename. "COM1.BAS", for example, will cause the behavior.

QuickBASIC attempts to access the DOS device "comX" and delays until
the device times out. Similar results can occur when you use other
device names. Using the DOS device name CON causes QuickBASIC to hang.
To avoid this, do not use the DOS device names as base names for your
files.

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