SCAT Purpose ======= The main purpose of SCAT is to clean up after FastBack Plus. FastBack Plus destroys the BPB (Boot block) of a normal DOS floppy disk. To many programs such a damaged diskette will masquerade as normal, but to others it will not. If you were to use these disks for normal DOS purposes, you would sooner or later get erratic results possibly losing your files. There are two ways to decontaminate FastBack Plus diskettes to make them suitable for DOS use again -- reformat them or use SCAT. If you are in any doubt whether a disk was ever contaminated by FastBack Plus USE SCAT. It won't hurt. WHATEVER YOU DO, AVOID USING FASTBACK PLUS DISKETTES AS DOS DISKETTES BEFORE DECONTAMINATION. SCAT has a secondary function of upgrading the boot track of floppies formatted under older versions of DOS. Some programs such as RESTORE, QDOS or BackIt may have trouble working with these older diskettes. SCAT has a third function of repairing a damaged boot block. SCAT has a fourth function of improving the error message you get when you accidentally try to boot from a non system floppy. If you change the message in SCAT.ASM you can customize the message. SCAT has a fifth function of telling you what sort of floppy you have -- how many sectors, how many sides, XT or AT style, and capacity. How to Use ========== Put the 5 1/4 inch floppy to be decontaminated in A: Type SCAT Follow the prompts. WARNINGS ======== If you were to type SCAT B: SCAT would STILL attempt to fix the floppy in the A: drive. SCAT always works on the floppy in the A: drive. SCAT is not designed to work on 3 1/2 floppies. DO NOT USE IT ON THEM. To SCAT, a valid 3 1/2 inch diskette is indistinguishable from a damaged 5 1/4 inch diskette. SCAT would attempt 5 1/4 inch style repair thus damaging your 3 1/2 inch diskette. FastBack Plus has some nasty habits, so even SCAT cannot always fully clean up after it. Watch out for partially formatted diskettes that were used as the last diskette of a set. These have to be reformatted. The fastest way to reformat is to use BackIt -- FastBack Plus's competitor backup program from Gazelle Systems in Provo Utah. SCAT has only been fully tested on cleaning up after FastBack Plus running on an XT. I would appreciate feedback on how successful it is at cleaning up after FastBack Plus running on AT-style diskettes. FastBack Plus is a totally different program from FastBack. Old FastBack used completely non standard diskettes that could not possibly be confused with DOS diskettes. The only way to prepare such diskettes for reuse is to reformat them. SCAT won't help. How SCAT Works ============== SCAT works even if the Media descriptor byte is damaged and even if the existing BPB (boot block) is totally trashed. It does not change the FAT or directory, so usually all files on the floppy will be recovered. Here is our overall strategy to reconstruct the BPB. 1. We read the boot record bypassing DOS to determine the media descriptor byte. If it is undamaged, we can reconstruct the rest of the BPB. 2. If the media byte is damaged, we might ask DOS its idea. The problem is, DOS will crash with divide overflow if it starts to interpret a mildly damaged BPB. So we read the FAT instead and look for the media byte at the head of the FAT. 2. If that does not work we ask DOS what the default BPB is for the device. 3. Reconstruct the rest of the BPB from the media byte. 4. Read track 0 to see what is there now. 5. Warn user if we will actually be changing the BPB. 6. Ask the user for final confirmation before fix. Author ====== SCAT is in the public domain and may be use for any purpose except military. Please report bugs and problems to: Roedy Green Canadian Mind Products 1150 Homer Street Vancouver BC Canada V6B 2X8 (604) 684-6529 Electronic mail users can contact me on: BIX id ROEDY ENVOY id ROEDY COSY id ROEDY WEB id ROEDY CATALYST id ROEDY GREEN SCAT was based on Peter Fletcher's copyrighted FIX_BPB program. For the curious, SCAT is not an acronym, it refers to the word "scat" as is "scat cat" referring to the FastBack cheetah cat logo.