phco@ecsvax.UUCP (John Miller) (05/19/87)
In article <231@grinch.grinch.UUCP> luis@grinch.UUCP (Luis Chanu) writes: >In article <3156@ecsvax.UUCP> phco@ecsvax.UUCP (John Miller) writes: >>. . . , but formatting >>destroys all data on a disk. > >I have to dis-agree with you John. I have used Mace Utilities, and it >can recover a formatted diskette (hard or soft). . . >------------------------------------------------------------------------------- I tested my first opinion by copying several files onto a floppy diskette, checking that they were intact, then formatting the diskette, then scanning the diskette with the low level edit feature of PC-Tools. Just as I thought, the entire data area of the diskette had been rewritten with constant values (F6h), the directory area was zeroed, and the only meaningful information apparent was the boot record. If Mace Utilities or any other program can recover from this situation, I would love to hear how they do it. Would someone else please repeat my experiment and let me know if I'm nuts on this? -- John Miller (ecsvax!phco) Dept. of Pharmacology, Univ. of N.C.-Chapel Hill Chapel Hill, NC 27514 (919) 966-4343
darrylo@hpsrlc.HP.COM (Darryl Okahata) (05/20/87)
In comp.sys.ibm.pc, phco@ecsvax.UUCP (John Miller) writes: > In article <231@grinch.grinch.UUCP> luis@grinch.UUCP (Luis Chanu) writes: > >In article <3156@ecsvax.UUCP> phco@ecsvax.UUCP (John Miller) writes: > >>. . . , but formatting > >>destroys all data on a disk. > > > >I have to dis-agree with you John. I have used Mace Utilities, and it > >can recover a formatted diskette (hard or soft). . . > >------------------------------------------------------------------------------- > I tested my first opinion by copying several files onto a floppy diskette, > checking that they were intact, then formatting the diskette, then > scanning the diskette with the low level edit feature of PC-Tools. Just > as I thought, the entire data area of the diskette had been rewritten with > constant values (F6h), the directory area was zeroed, and the only > meaningful information apparent was the boot record. If Mace Utilities > or any other program can recover from this situation, I would love to hear > how they do it. > > Would someone else please repeat my experiment and let me know if I'm nuts > on this? No, you're far from nuts; in fact, you're quite sane ;-). That is exactly what is supposed to happen when you format a floppy disk. When you buy a brand new floppy disk, the disk contains no address marks (used to find sectors on a soft-sectored disk, which is what is used by IBM PCs) or data. The act of formatting the disk places, on each track, the following information (this is a simplified description): <address mark> <data> <address mark> <data> <address mark> <data> ... where "<address mark>" is data describing the address (head (?), track, and sector number) of the following sector of data ("<data>"). The address mark is a very essential piece of information; without it, the floppy disk controller would not be able to find sectors on a disk. For IBM PC disks, 8 or 9 pairs of address marks and data are placed on each of the 40 tracks. As it isn't possible to write address marks without writing a corresponding data sector, the act of formatting, which writes address marks, also writes data, effectively erasing all information from the disk. As you've found out, each sector is filled with some constant value (0F6H). > > > -- > John Miller (ecsvax!phco) > Dept. of Pharmacology, Univ. of N.C.-Chapel Hill > Chapel Hill, NC 27514 (919) 966-4343 > ---------- -- Darryl Okahata ucbvax!ucbcad!ames!hplabs!hpcea!hpsrla!darrylo <== best path hplabs!hpcea!hpsrla!darrylo <== alternative CompuServe: 75206,3074 Disclaimer: the above is the author's personal opinion and is not the opinion or policy of his employer or of the little green men that have been following him all day.