Q123687: Enabling CTRL+C and CTRL+BREAK by Using PeekcharQQ

Article: Q123687
Product(s): Microsoft Fortran Compiler
Version(s): 1.0,1.0a
Operating System(s): 
Keyword(s): 
Last Modified: 03-NOV-1999

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The information in this article applies to:

- Microsoft FORTRAN PowerStation for MS-DOS, versions 1.0, 1.0a 
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SUMMARY
=======

To break out of a long running program, it is customary to use CTRL+C or
CTRL+BREAK. However, MS-DOS only checks for CTRL+C or CTRL+BREAK when processing
keyboard input. If there is no keyboard input in a loop (it contains only
calculations), the program is likely to ignore CTRL+C and CTRL+BREAK.

The PeekcharQQ() function performs keyboard input processing and should not
significantly slow down your program, if used cautiously.

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

When you call PeekcharQQ() in a long loop, MS-DOS checks the keyboard for input.
If CTRL+C or CTRK+BREAK was pressed, the program terminates.

In the sample code in this article, PeekcharQQ() is called thousands of times a
second. In an actual application, this would noticeably slow the program. It is
usually sufficient to place calls to PeekcharQQ() so that it is called at most a
few times a second.

NOTE: Sometimes the following simple code will break on a CTRL+C even without the
call to PeekcharQQ(). However, more complex code will require adding calls to
PeekcharQQ() to allow CTRL+C or CTRL+BREAK processing.

Sample Code
-----------

  C Compile Options needed: none

        include'flib.fi'
        include'flib.fd'

        logical l

        do i=1,1000000
           x = sqrt(i)
           l = peekcharqq()
        end do
        end

Additional query words: kbinf nofpsnt 1.00 1.00a

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Keywords          :  
Technology        : kbAudDeveloper kbFortranSearch kbZNotKeyword3 kbFORTRANPower100DOS kbFORTRANPower100aDOS
Version           : :1.0,1.0a

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