Dear Dr. Holt,

As for your question

I have on several occasions found it annoyingly difficult to save data from
a GAP session in a form in which it can be read straight back in again in
a later session. Is there some straightforward way of doing this, which
I do not know about?

This morning I was close to panic. Some wretched safety officer wanted to
check all of the electrical fittings in my office, which meant shutting
my Workstation down, and it had just spent all night calculating and
simplifying an enormous subgroup presentation. However, I came up with
the following procedure for saving my presentation in a GAP-readable form.
Is there any easier way?

In the special case of just having to save a subgroup presentation you
could have used the Save command for presentation records:

Save( "filename", PresentationFpGroup( G ), "P" );

Then, in the next session, you may restore the presentation again by the
commands

Read( "filename" );
G := FpGroupPresentation( P );

Martin Schoenert will answer your question how to save data in more
generality.

Best wishes, Volkmar Felsch