Author: Havoc (proxy.gelrevision.nl)
Date: 09-23-1999 15:25
.ST and .MSA files are so called "disk-images". As you might know, several games and demos on the Atari platform used a diskformat of their own, so that crackers and idiots would have a harder time doing things the gamecompany didn't want them to. It's impossible to see separate files with (for instance) TOS/GEM, so if you'd want to copy such a game, you'd have to find a way to copy the whole disk instead of just a couple of files. Hardware copiers were one of the first possibilities to do this.
But if you want to transfer such games through a BBS system or the Internet, you'll have to put it in a file. That's when people came up with the idea of making a file that would contain every single bit of data that was on a disk, plus ofcourse some data on what number of tracks/sectors etc were on the disk. This way, it was dead easy to transfer files through networks. The most used format for this purpose was .MSA. .ST came around when Pacifist was launched I think, but it's the same idea.
Nowadays, MSA or ST are also used because it's easy. Just put the disk in your drive, run MSA and there you go, one single file with all the stuff you need inside. It's even being used for "normal" disks.
Why zip/lzh those files? Well, most of the time, disk images are unpacked. So they can get a lot smaller by using a packer.
To use MSA files on a normal Atari, get the Magic Shadow Archiver. For ST files, get ST2Disk.
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