Action Taken on Abort, Retry, Ignore, Fail

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Summary
This article explains the actions that MS-DOS takes when a critical errorhappens during a disk access. MS-DOS takes specific actions for each of thefour possible Critical Error (Interrupt 24h) responses: Ignore, Abort,Retry, or Fail.
More information
According to the "MS-DOS Encyclopedia," MS-DOS takes the following actionsfor each possible critical error response.
   Error     Action   ----------------   Ignore    The MS-DOS function call returns to the application             program as if the function had completed successfully.             For example, if the program is trying to read from the             disk, MS-DOS tells the program that all is well. This             can result in corrupted data in your disk file or             in data returned to your application.   Retry     The critical error handler signals MS-DOS to reissue the             last function call made to the device that caused the             critical error.   Abort     The current application is terminated immediately.             Unwritten disk buffers are NOT written to disk, the             directory information is not updated, and modified             interrupt vectors are not reset. Choosing this option can             leave the system in a very unstable state.   Fail      This causes MS-DOS to return to the application software>             with an error condition. In programming terms, the carry             flag is set upon exit from the INT 21h DOS function call.             This allows the application program to handle the error             itself and take appropriate action, rather than letting             MS-DOS do it.				
The MS-DOS kernel and device drivers do not mark a FAT entry as being badwhen a critical error occurs, or at any other time. This task must be doneby a separate utility. The RECOVER utility provided with MS-DOS can dothis, but only if the bad sector exists within a file's allocated clusters-- free bad clusters are not checked by RECOVER. The FORMAT utility istypically the best solution, since it scans all areas of the disk for badsectors. The disadvantage is that FORMAT also destroys any data on thedrive.

Some third-party disk utilities provide disk-scanning features that examinethe entire disk data area for bad sectors, and then mark them as bad in theFAT (without disturbing other data on the disk).
6.22 3.20 3.21 3.30 3.30a 4.00 4.01 5.00 5.00a 6.00 6.20
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Article ID: 67586 - Last Review: 10/26/2013 12:22:00 - Revision: 3.0

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