The open file command opens, reads from, writes to, or creates text files
on your Macintosh. HyperCard has a limit of three open files at one time.
Although this limitation is documented in the book "HyperTalk 2.0" by
Kamins and Winkler, they wrongly inform the user that when a fourth file is
opened an error message will appear: "Can't open any more files." They go
on to say that when the user clicks the error dialog away, the open files
will close, allowing any other files to be opened/created. This is not
the case. The dialog never shows.
HyperCard displays an error message only when it tries to write to, or
close a file (the fourth on...). "File not open." It will not alert you
that your fourth file couldn't be opened in the first place.
Users must be careful to balance their opened files when writing scripts
that use this command extensively.
This article is adapted from the Claris Tech Info database.