re-entrant programs

[dockery@griffin.cuc.ab.ca (Sean Dockery)]

This is a repost of a message which (should have) appeared on
comp.sys.apple2 a little while ago.  I received no responses to the
message so I can only assume that it was lost in the internet.

---repost starts---

I have often heard the term describing software to be "re-entrant."
The context under which I have heard it most used was an opinion that
the Apple IIgs tools and GS/OS would be easier to work with if they
were re-entrant.

Would someone please enlighten me with the answers to the following:

	o What qualifies an application as re-entrant?
	o What are some examples of re-entrant software?
	o What are some advantages and disadvantages of an application
	   that is re-entrant?
	o Are re-entrant applications significantly larger that
	   others that perform the same task?

Thankyou for your time.

---repost ends---

I have managed to elicit responses from a few friends that a
re-entrant program or routine ``makes no assumptions about the
variables it uses,'' which I have interpreted to mean that a job can
be interupted and resumed without any adverse effects by calling an
specific entry point in the routine.  Is this correct?

If it is, doesn't that simply mean that a dispatcher should handle
variable initialization and call the desired routine while direct
calls to the routine (or an entry point therein) with variables
predetermined (left untouched from a previous call) for that routine
will just enable the routine to continue its unfinished task?