Path: utzoo!telecom-request Date: 9 May 91 14:31:23 GMT From: Jeff Wilkinson Newsgroups: comp.dcom.telecom Subject: Re: Prodigy or Fraudigy ??? Message-ID: Organization: Medtronic Inc, Minneapolis MN Sender: Telecom@eecs.nwu.edu Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 351, Message 5 of 10 Lines: 31 In article binder@decvax.dec.com (Simplicitas gratia simplicitatis) writes: > Toby Nixon writes: >> ... even formatting a disk does not remove old information! > I beg to differ. Vehemently so. I used to design controllers for > both floppy and hard disks - I did it for about 14 years, using SSI > The formatting operation must by its very nature destroy the old data. > Formatting is a write operation that is done without reading to verify Well, your both right. Formatting, at the controller level does destroy everything on the disk (at least as far as mere mortals are concerned. The NSA claims that its just a minor incovenience). However, DOS only does a low-level format on flexible disks. Hard disk "formatting" consists of a read test of every sector and a rewrite of the FAT (ever wonder how Norton and other utilities can advertise disk recovery, after a format?) No actual media format or writeover is done. Therefore, information on a hard disk is still available to determined disk hackers, after a format. It takes special disk utilities to do "low-level" formats on a hard disk (the BIOS knows how, but DOS doesn't). Some hard disks, notably those from Plus Development Corp, give you a warning message and halt the machine if you try to do a "low-level" format. Thus, Toby's right, DOS doesn't always clean up a disk with a format. But Dick's write [sic] too. The controller makes toast of your data.