CHKDSK is a program shipped with all versions of MSDOS. CHKDSK reports the amount of free space on a disk and also the amount of "low memory" available. CHKDSK also checks for and optionally corrects many structural errors in the layout of disk data. The Free space reported by CHKDSK is Unused Sectors times 512 bytes. It is the same as the "bytes free" reported by DIR. The disk space reported must be divided by 1048576 to get to the "megabytes" reported by FDISK. CHKDSK checks for and optionally corrects for disk data structure errors -- primarily lost clusters and cross linked files. Lost clusters are a normal phenomenon that can occur when MSDOS is abnormally terminated. . Cross linked files are a serious and abnormal problem that gets worse with time if not corrected. CHKDSK error correction other than lost clusters is relatively unsophisticated. Many people recommend that errors be corrected with the more sophisticated tools found in commercial packages such as Norton Utilities, although there is some question whether the difference between "bad" (CHKDSK) and "good" is all that great. It has been reported that CHKDSK arbitrarily fixes certain obscure disk structure errors in non-optimal ways even though the F (Fix) parameter is not used. Starting with DOS 5.0, Microsoft has been shipping a tool called SCANDISK acquired from a commercial package and has recommended its use in place of CHKDSK.
Disk diagnostics such as CHKDSK or SCANDISK should not be run if disk drives are not working properly or similar software problems are suspected. If data is not being read/written to/from disk properly, trying to fix the incorrect data may cause serious problems.
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Copyright 1994-2002 by Donald Kenney.