STAC is a custom tape system I designed in the mid 80's. It was very popular in South America and spawned a myriad of clones, mostly at Chile, where Atari was very strong. Note that most clones just reused the main concept, and not copied the actual implementation.
STAC stands for Super Turbo Auto Corrector in Spanish. Is has a software turbo. But I learned soon enough that the reliability of the turbo depends on many external factors. So STAC implements other features that I considered even more important.
The key feature in STAC was error recovery. The Atari tape system is slow enough that it is almost unbearable to wait until some software finishes loading. But worse than this was being very close to complete the loading and suddenly getting a load error. You had to rewind and start all over from the beginning. At this point what you really wanted is to throw the tape, the recorder, and even the computer out of the window.
To avoid this, STAC implements a simple error recovery. If the loader detects an error the user is prompted to rewind just a little bit. The loader then resyncs with the tape, hopefully this time the error is not repeated, and continues loading. Most errors are typically soft errors and the retry logic works very well.
STAC also implements a simple zero cost RLE compression. The data is decompressed on the flight while loading. I was amazed how much this saved in some cases.
Finally, although not strictly a STAC feature, I adapted for tape several titles that were available only on disk.
Edited by ijor, Tue Jul 4, 2017 9:17 PM.