Re: Applesoft/Prodos/ONERR GOTO/File existence question

[Ed Eastman <ed@apple2.com>]

If you are running in DOS 3.3, then the verify command was what was
recommended to make sure a file exists.  (IIRC)  Error trap the Verify 
command then turn the onerr flag off and continue your program.  Break 
points are better for verifying program execution than onerr.

It also sounds like you may be getting an error (even a Control-C) from 
somewhere else inside your program that is not a subroutine. Your onerr 
routine was only designed for the file issue.  This too may cause the 
symptom you are having.  Try clearing the onerr flag after you read the 
maze file.

Also working with text files in DOS 3.3, there was an error with the 
file handles not working quite properly when a program exits 
prematurely.  Add a CHR$(4)"CLOSE" to the front of your program to clean 
the file handles up 'before' you run your BASIC program and see if that 
doesn't help.  (I remember lots of issues debugging EAMON games.)

Thankx,
Ed