Large data file crashes program

[Fred Lampart]

I've developed a Powerbasic DOS program that reads a data file,
manipulates the data, prints the results to the screen and then
offers the option to print hardcopy.

Everything works great until the data file gets too large ..
When that happens the program hangs and I have to CTRL ALT DEL
to get back to a DOS window.

The data is read into a 2 dimensional string array thats
dimensioned adequately early in the the program.

What should I check first? Second? Third?

I'd also like to trim the program size by getting rid of LPRINT
code that identical to the PRINT coding. The former is only used
to allow printing hardcopy after the information has been
printed to the screen.

Can I somehow offer the hardcopy option without cycling the
program thru similar LPRINT coding? The LPRINT coding adds
greatly to the program's size, so I'd really like to try
other options.

Thanks for any ideas...

[G Grant]

If you want to use the same code to print to either the screen or
the printer (or both), you could use PRINT # in place of PRINT and
LPRINT.

OPEN "CONS:" FOR OUTPUT AS #1
OPEN "LPT1:" FOR OUTPUT AS #2

Then you could print to the appropriate device using the same code:

PRINT #1, "This is on the screen"
PRINT #2, "This is on the printer"

Just use a variable in place of the device number to use the same
line of code for multiple devices.

As for large files hanging your computer, have you tried using
VIRTUAL arrays? You can't use variable length strings with VIRTUAL
arrays, but you can use ASCIIZ strings. ASCIIZ strings work much
like variable length strings, but with a set length limit. Just
determine the length of the longest string you might need, and then
create a virtual array of ASCIIZ strings of that length. Then you
would use them just like you would use variable length strings.

DIM VIRTUAL MyArray(100, 100) as ASCIIZ * 1000 '10 meg array

Just make sure the entire array doesn't exceed 16 meg (32 meg in pure
DOS mode with some memory managers). You can have multiple arrays,
each up to 16 meg, without a problem.

If you decide to try it that way, I wrote some code a while back
to load and save VIRTUAL arrays of any size and type to disk VERY
fast, using ASM. If you want to try it, let me know and I'll post
it here.


------------------

[Lance Edmonds]

On the subject of "crashing the PC" when the datafile gets large, I have to ask: Have you enable all types of error checking in your code? Simply add a $ERROR ALL ON meta-statement to the top of your code.

By default, PB/DOS does not add error testing code to your application for such things as array boundary testing, overflow, etc.

There are also other things that can crash your program that error checking does not catch - using pointers incorrectly, badly written inline-assembly, etc. These are "soft" errors that can cause memory to be overwritten or altered, and their effects may not show up immediately - the error may show up hundred or thousands of lines of code later in your application.

In summary, retest your code with $ERROR ALL ON and see how you get on. If you are still having problems, start eliminating sections of your code until the error goes away. Don't delete the code out though - use REM on individual lines or $IF 0 | $ENDIF meta-statements to 'mark' a whole block of code as a comment.

for example

PRINT "THIS PRINTS!"
$IF 0
PRINT "THIS IS IGNORED BY THE COMPILER"
X& = X& \ 0 ' this would be an error if executed!
PRINT "See? I'm really a comment that looks like code!"
$ENDIF
PRINT "This prints too!"

Also, the debugger can be handy to track down this type of problem. Let us know how these suggestions help you solve the problem.


------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>