Microsoft KB Archive/49692

PRINT Doesn’t Always Work When Sending Output to COM Ports PSS ID Number: Q49692 Article last modified on 07-14-1993 PSS database name: O_MSDOS

3.30 4.01

MS-DOS

Summary:

Microsoft has confirmed that a PRINT problem occurs in MS-DOS versions 3.30 and 4.01. The following steps can be used to reproduce this problem:


 * 1) Connect a serial printer to COM1: or COM2:.
 * 2) Boot MS-DOS Version 3.30 or 4.01.
 * 3) Enter “C> MODE COM1:9600,n,8,1”.
 * 4) Enter “C> PRINT AUTOEXEC.BAT”.
 * 5) Select COM1: as the device to print to.

Printing does not occur. To print properly, you must enter the following command before entering the PRINT command (Step 4):

C> TYPE filename > COM1

“filename” is some nonempty file, such that at least one character is sent to the printer. This seems to “prime” the COM driver so that PRINT will work when invoked.

This problem does not occur in later versions of MS-DOS.

Additional reference words: 3.30 4.01 noupd

Copyright Microsoft Corporation 1993.