PE> Let's assume I was writing Zmodem in an object oriented language.
PE> What are the applicable objects here?

PE> Is there a Zmodem object, with two operations, send() and receive()?

PE> Is there a send object with an operation of zmodem() and another
PE> operation of sealink() and another operation of xmodem()?

PE> Are zmodem send and receive simple operations, like patmat()?

PE> Are zmodem send and receive two separate objects, both with one
PE> operation, perform()?  [this is what I think is the solution at this
PE> exact instant of time].

The most obvious consideration is the question of bidirectional protocols.
If you dont allow for that in that design stuff you are considering now,
that can rule out allowing that in the future without a complete change.

PE> The zmodem send and receive have some code that is common to both.

Not relevant to what it looks like to the higher level code.

--- PQWK202