TRS-80 Question

[Eric Dittman]

On 4/12/22 6:37 AM, Bill Gunshannon via cctalk wrote:
> So, this just gets more and more confusing. (Have I really been away
> from all this for that long!!!)
> 
> I dug up the tech manuals for the two of them (buried deep in my
> stacks of books) and compared them.  And you are, of course, right.
> 
> Which just brings more questions.
> 
> Why do Model I cassette programs (not BASIC) not run on the Model III?
> Why did they relocate a Model I program that had a specific Model III
> version to a slightly higher location in memory?

It was common to add a loader for cassette programs that would
load the program in higher memory and relocate to the original
location so they could be loaded from disk (on both the Model I
and Model III).  This is because the original location would
typically be in low RAM used by the OS.

In some cases there wasn't a disk version of the program, in
other cases it was to avoid having to buy the disk version.
For games if there was a disk version the only likely change
was to add a high score table that was written to disk, so
not worth paying again.  There were a few games that added
extra features to the disk version but right now I can't
remember which ones.  I think Big Five did a few this way.
-- 
Eric Dittman