Q35667: OP Parameter Fails to Make OPEN "COM1:" Wait Indefinitely

Article: Q35667
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | docerr B_BasicCom | mspl13_basic
Last Modified: 12-DEC-1989

The manuals listed below incorrectly state that if the OP serial
communications parameter is specified without a value, the OPEN COM
statement will wait indefinitely for the port to be opened. The OPEN
COM statement will actually wait only 10 seconds.

This correction applies to the following manuals on Pages 298 and 299:

1. "Microsoft QuickBASIC 4.0: BASIC Language Reference" manual for
   Versions 4.00 and 4.00b

2. "Microsoft BASIC Compiler 6.0: BASIC Language Reference" for
   Versions 6.00 and 6.00b for MS OS/2 and MS-DOS

This error also occurs on Page 255 of "Microsoft QuickBASIC 4.5: BASIC
Language Reference" for Version 4.50.

This error has been corrected in the Microsoft BASIC PDS Version 7.00
documentation.

Code Examples:
-------------

The following program demonstrates that you still get a time-out using
the OP parameter:

DEFINT A-Z
PRINT "wait for open"
OPEN "com1:19200,n,8,,OP,rb4048" FOR RANDOM AS #1
PRINT "opened"
.
.
.
END

As a workaround, you can use the following program, which will wait
indefinitely with the error handler returning to the OPEN COM line
until it is opened:

ON ERROR GOTO check
trial = 0
OPEN "com1:9600,n,8,,OP,rb4048" FOR INPUT AS #1
PRINT "opened...."
END
check:
        IF ERR = 24 THEN
                trial = trial + 1
                PRINT "open attempt#"; trial
                RESUME
        ELSE
                PRINT "fatal error abort"
                END
        END IF

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