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

On Tue, 24 Jun 2003 07:32:35 GMT, CBFalconer <cbfalconer@yahoo.com>
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