Copyright 1991, P. R. Fletcher
In addition to its testing function, HDTEST has been reported to be useful as an automatic disk repair utility for both hard and floppy disks which have developed (especially) intermittent or persistent read errors, preventing or impeding their normal use. Although HDTEST cannot read the totally unreadable, it tries much harder that DOS does and will almost always, in the course of its operation, allow you to recover the entire readable portion(s) of a file with one or more unreadable clusters in it, optionally either remapping all of what it reads from the disk or replacing bad sectors (the default) or clusters with NULLs.
HDTEST is not an alternative to backing up your floppies and/or hard disk -- it may sometimes be able to save your neck when you forgot or your backup went bad too! On hard disks which have developed intermittent read errors, running HDTEST can sometimes totally cure the problem, presumably because the "flaky" sectors get rewritten and the minor misalignments and/or weakening of the magnetic "image" which were causing the trouble are corrected when the data is rewritten.
In its default ("slow") mode, HDTEST writes 20 different test patterns to every cluster on the disk and checks that each pattern can be read back correctly, while preserving (and eventually restoring) the contents of the clusters that contain data. HDTEST can even (on many devices) detect hard disk errors which are minor enough to be correctable (and corrected) by the disk controller's own "error- correcting code" (ECC). These errors are normally totally invisible to programs running under DOS and will not usually be picked up by other disk test utilities. They may, however, be early signs of problems that will become significant later, and HDTEST consequently marks these clusters, too, as bad. As long as HDTEST can read the data from a flaky cluster correctly once (and it tries quite hard) it will be able to save the file of which that cluster is a part intact, while marking the cluster so that DOS does not try to use it again.
The program was designed to minimize the likelihood of user error causing data loss on a good (or slightly bad) disk, and to be as easy as possible to use. It could not be made very fast, since multiple bit patterns have to be written to and read from each cluster, and this takes a significant time even on a fast hard disk. The program does, however, have a less sensitive "fast" test mode, which writes only two test patterns to each block and is recommended for use when testing/repairing floppy disks and/or to correct intermittent problems or rule out gross problems on a hard disk.
The program can be used to test/repair single and double-sided 8- and 9-sector minifloppies (if you have plenty of patience!), as well as AT-format 1.2Mb minifloppies, 8" standard floppies, and 3.5" microfloppies (with the same proviso regarding a need for patience).
HDTEST's companion program, HDCHEK, simply examines the logical structure of the system and target device and gives a short report on what it finds. It does not write to the disk, and is provided principally to allow a quick and easy, but fairly reliable, check on the compatibility between HDTEST and a given software/hardware configuration. As part of its report, HDCHEK notes at what level (DOS interrupts only, INT 13, or direct entry to the BIOS) it was able to access the target device, which has a bearing on HDTEST's ability to detect certain types of errors. In general, if HDCHEK runs successfully on a system and target device, then HDTEST can be expected to do so, although the latter program requires much more available memory.
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Theft by deception as a way of life . . .
Hudson County Facts |
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As Described By Rutgers University’s Bloustein School of Planning and Public Policy |
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The 2001 Race for Governor of New Jersey |
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New Jersey Fact: "New Jersey is a small state on the eastern seaboard halfway between Honest John Lindsay and the Liberty Bell. It is best known for its turnpike, Atlantic City, Imamu Baraka, Newark Airport and the Morro Castle disaster. Most of its leaders are in jail for stealing money...." Over thirty years ago, this was how a New York Times writer described New Jersey. The only things that have changed are that now Bloomberg has Lindsay's old job and Amiri Baraka figured out somewhere along the line that it's not too swift for an atheist to use a religious title. |
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Political corruption is a tradition here.
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