The infinitely profitable program

Tapley, Mark mtapley at
Tue Jul 5 09:22:44 CDT 2016

On Jul 2, 2016, at 1:37 PM, Fred Cisin <cisin at> wrote:

> On Sat, 2 Jul 2016, Eric Christopherson wrote:
>> Genius.
> Clever? yes.  Genius? no, or you would have to count too many of us.
>> But I would have thought CP/M would at least require a .com file to
>> have a header.
> NO.
> A .COM file is a pure image of memory, starting at location 100h.
> The "header" or "zero page" or "program segment prefix" is generated on the fly during the loading of the program.
> (There is a lot more to know about it)

Fred, I tried for years to understand the difference between .COM and .EXE. One post of yours, and it’s clear. Thank you!

> The first thing that I did in CP/M was to create a zero length program. it seemed intuitively obvious as a needed capability.
> Didn't everybody realize that and do it?
> It never occurred to me to try to SELL it!  In those days, there was almost an assumption that price would be proportional to program length.

I would urge caution in this regard. Depending on the distribution of the dots on the price/length plot, it’s not inconceivable that a least-squares fit would result in you having to PAY people to accept your program, depending on where the line crosses the “price” axis ….

> For those who wanted "source code" for it:
> (SAVE was one of the five CP/M internal commands, ERA,REN,DIR,TYPE)

…. uh oh. Too late.

								- Mark

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