[Coco] "Which language for teaching Computer Science?"

[Gene Heskett]

On Sunday 29 January 2006 22:23, Jim Cox wrote:
>I cam across this posting on digg.com and though it might
>be of interest to some of you out there:
>
>http://directorblue.blogspot.com/2006/01/which-language-for-teaching-c
>omputer.html

Interest?  Lets just say that I cut my programming teeth in hex codes by 
looking it up in the programmers manual for an rca 1802.  My first 
program laid a new academy leader on a commercial along with the 
required trigger tones to control an automatic station break machine we 
had at KRCR-TV in Redding CA. It worked so well that it was used 
non-stop for more than a decade after I'd gone down the road.  The code 
was just over 1180 bytes IIRC, and I still have a copy it it someplace.
Aproximately 580 bytes of code, and 680 bytes of lookup tables, all kept 
in battery backed static ram.

I was concerned that since it had to do its thing for every tv field, it 
might not be fast enough, but a flag I could watch with a scope 
confirmed that the program had executed and reached the waiting point 
for the next field by line 22 of the field.  Video I generated by a dma 
to the video generators register, a very simple scanner because it 
needed to generate video that could be read on a 5" monitor from 15 
feet away in the control room.  Only 6 bytes per field serviced the 
video generator.

Yup, if you want it to work right, and not waste any time in compiler 
garbage, machine code (assembly if you have the assembler) is the 
answer.  And yet that code made use of subroutines that weren't 
supported on that cpu except by canned routines that took 22 cycles to 
execute the call, and 29 cycles to execute the return IIRC.  With a 
clock speed of .889 mhz, and 8 cycles per machine cycle, the impression 
was that it was slow, but for that it turned out to be plenty fast 
enough.

When I found the coco, and os9, I brought that experience to the 6809, 
and some of my code is still in use.  The secret was that the coco was 
also 'accessable' unlike the TI99-4A that preceeded it on my worktable.

-- 
Cheers, Gene
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