Re: How to store a checksum value at end of file?

Discussion in 'C Programming' started by Dave Thompson, Jul 4, 2003.

  1. On Tue, 24 Jun 2003 07:32:35 GMT, CBFalconer <>
    wrote:
    [re CRC-izing program]
    > The /t switch inserts an 0x1a EOF marker in a file before
    > appending a checksum. For systems that respect this (standard)
    > EOF marker it avoids confusion. Unfortunately checksum removal
    > with the /r switch will not remove that EOF marker and the MS
    > internal filesystem does not necessarily signal EOF on
    > encountering it in a disk file. Just another Microsoft bug.


    'standard'? Say what? I know of no standard making 0x1A EOF,
    or systems using it so other than RT-11 and I think RSTS/E (now
    effectively gone) and PCs. If you wanted an ASCII-standard EOF,
    the closest approximation would be 0x19 End of Medium or
    0x1C File Separator. There are standard tapemarks for magtapes,
    but they are out of band, not a character code.

    And TTBOMK all MS filesystems have had exact byte counts,
    and thus not needed an EOF character. It was CP/M that didn't,
    and early PC applications (and C implementations) supported it for
    portability, and still do for tradition and/or bug-compatibility.

    Well, XMODEM also had block granularity and needed an EOF code;
    I don't remember if it used 0x1A though. That was an important and
    influential utility, though not a system as such.

    - David.Thompson1 at worldnet.att.net
    Dave Thompson, Jul 4, 2003
    #1
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