Ken's DEFT Pascal Page
Updated September 3rd, 2000 

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DEFT Pascal

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I first started using the Tandy Color Computer in 1982, and I soon upgraded my old grey cased coco to 64K with a disk controller. I purchased DEFT Pascal at a Rainbowfest in New Jersey, and was soon using it to port a graphics package I had written for the Apple ][. The Mac was just coming out, and I wanted to be able to write programs that looked like the Mac.

The graphics package started out as a side project under Apple Pascal to allow me to write an address book program. The Apple Pascal package had the normal graphics routines for the times - it could draw lines, write text, and not much else. I wrote software to allow menus and non-movable windows. The address book program was popular with my co-workers, but I never released it to the general public.

In 1982 I purchased the Tandy. In 1984 I sold my Apple computer. I had contemplated a Macintosh, but didn't for two very good reasons - my newly arrived twin sons. Since I only had the Tandy computer now, I decided to port the software I had written to it. First on the list was the address book, and that needed the graphics package.

DEFT Pascal had many things going for it - but graphics wasn't one of them. I ended up writing a complete set of low level primitives for text display, line drawings, and the like to be able to implement the graphics package. After some long nights, I finally had everything working to my satisfaction. Friends with the local computer club encouraged me to submit it to DEFT for possible publication. After discussing it with Dan Eastman (the DE in DEFT), I sent a demo disk to them for review. The were interested, and asked for a number of additions, such as flood fill routines. I finished these just in time for DEFT to exit the CoCo market.

Some months later I discovered that TCE had picked up the DEFT rights. I sent the the demo disk, made changes they asked for and the software was released as DEFT AGS (for Advanced Graphics System). All kinds of promotions and advertising was promissed - and never appeared. One news letter was sent to a few people, but sales were weak (as could be predicted). This was right when the CoCo 3 was coming out, but TCE had just pulled all of there ad's from Rainbow in a dispute, and my program was never promoted.

The CoCo 3 brought problems for DEFT - it wouldn't work. The default library used the FEXX page of memory that was now reserved. That was an easy change, but other problems cropped up. The biggest was releated to the disk controller. Sometimes, for no apparant reason, the disk controller would miss writing a byte to the disk, and the disk would become trashed. This problem was highly dependent on the disk controller and the location in memory that the code resided. I went so far as to clone the disk controller ROM into a RAM address - and was able to make it fail by shifting it one byte up or down. The code appeared to be sensitive to the odd/even address of the buffer. Once I understood this it was an easy matter to make the code self adjusting for the load address.

The CoCo 3 version of DEFT Pascal sold a few copies, but it suffered from two sales problems. One was the lack of promotion by TCE. The second was then inclusion of copy protection on the linker. TCE was concerened about software piracy, and was insisting on a copy protection scheme. I convinced them to protect only the linker (since if that wasn't working the rest of the package wouldn't do you much good). I then convinced them to use a copy protection method that would be fairly easy to defeat for a competent programmer, but yet couldn't be copied by the disk copiers on the market at the time.

In a nutshell, the copy protection uses the track past the last one on the disk. One of the sectors is missing from the track. The copy protection ensures that it can read a sector from the track, but that it can't read the known missing one. TCE called this Softlock, and used it on their BuisnessWriter product along with the DEFT Linker.

Since the copy protection prevents the use of the Linker in the CoCo emulator, you'll find a patched linker in the DSK image posted that contains the latest working version of DEFT that I have.

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