How is U2 different from XyWrite?

["John H. Kessel" kessel.1@xxxxxxxx]

When I posted my first questions on August 4, I said I was a low-end user.
Let me
amplify that. I have read that John Tukey distinguished data analysts from
statisticians. In the same spirit, I am a program user, not a programmer.
Right now,
for example, I learn a little bit more about U2 each time I reread the
documentation
and especially when I use a command for the first time, but in the end it
doesn't add
up to very much. All I need to know are how to issue the commands, and have
some
general sense of what a program does.
I spelled this out because I want to ask a question so general that a
complete response
would require hundreds, if not thousands, of pages. Both native XyWrite and
the
entries in U2 are written in XPL. So how are they different? More
specifically, we are
dealing with at least five entities: original XyWrite 4.016, U2, Virtual
Dos Machine, an
Operating System, and other applications that run under that OS . PARSEFRM.DOC
explains that U2 makes XyWrite much more efficient by loading all needed
commands
at one time, thus preserving memory. But there has to be interaction
between XyW and
VDM, the OS, and any other applications involved. Does U2 "translate" the
XyW output
so it can be understood by the "external programs?" "Translate" commands
from the
"external" programs so XyW can respond to them? Or is its fundamental task
something
different?
All I am looking for is a reply of paragraph length. I understand that this
would involve
gross simplification of intellectual work that has gone on for more than a
decade. But
it would help me begin to understand what's going on.

Thank you.

John


John H. Kessel
Ohio State University
kessel.1@xxxxxxxx