Monday, March 15, 2010

Wendin DOS and C

One of Bob's ideas about improving our shop floor tracking system was to purchase a bunch of very simple wall terminals and control them from a single computer. This was meant to be a very economical solution. Workers in each department would type in the job numbers and quantities and so no one would need to run around collecting data with a bar code wand. I thought this was a great idea, and I figured I could write something like this in C.

To make this work I would need to write a service routine to monitor the serial ports, and the application would need to essentially multitask. I used C structs to manage related bits of information and created routines to read and write data to disk files. The program would present a simple prompt for logging in, specifying a department and entering a job information.

This was all fine, but it was hard to add new functionality to the system, and I was finding it frustrating dealing with memory bugs and pointer related bugs.

I decided that I needed a multiuser system. If I took the multitasking out of my C code then my programs would be simpler. I noticed an ad in a magazine for a multitasking version of DOS called Wendin DOS. This version of DOS was based on a VMS architecture, and it was very inexpensive. I approached Bob and he bought a copy.

On my Tandy 1000SX Wendin DOS was sluggish. I hoped that this wouldn't matter much because if I could create a working system then we could buy a more powerful 80286 computer to run it on. I was able to create multiple sessions and run my C tracking system in them. Each of them ran in its own text window. This was amazing to me!

Now the bad news. Wendin DOS would crash without warning. The whole screen would suddenly clear and display a "guru" error message. Guru error number such and such. This was really weird. What was a guru, and why was it in my computer?

Some of the error messages were explained in the manual, but some weren't. It became clear to me that there was nothing I was doing to make this happen. I contacted the people at Wendin and even got a response, but they didn't fix anything.

Ultimately I had to give up on Wendin DOS and look for another solution.

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