On Jul 28, 2012, at 11:52 AM, Doug Ewell <[email protected]> wrote: > ^Z as an EOF marker for text files was part of the MS-DOS legacy from > CP/M, where all files were written to a multiple of the disk block size > (I think 128 for CP/M and 512 for MS-DOS 1.x), and there had to be some > way to tell where the real text content ended. New stream-based I/O > calls in MS-DOS 2.0 made this mechanism unnecessary. Unix systems had no > legacy from CP/M, so they never had this problem.
Worse than that, actually. Actual MS-DOS APIs from 1.0 on were able to handle the situation, but the MS-DOS BASIC language and interpreter, with CP/M roots, assumed the 128-byte sector, and therefore demanded the ^Z. It was fixed as early as 1.1, I think, but the malady lingers on. >> I.e., this is why we do have this messy text OR binary file I/O >> distinction like O_BINARY (for open(2)), "b" (for fopen(3)) or >> binmode (perl(1)). Because without those a text file will see >> End-Of-File at the ^Z, not at the real end of the file. > > The reason for the text/binary distinction on DOS and Windows is > conversion between Unix-standard LF and Windows (DOS, CP/M)-standard > CRLF. It might be true that library calls to read a file in text mode > will stop at ^Z, but Notepad and Wordpad don't. I know the library > doesn't automatically write ^Z. Almost nobody in the MS world uses the > ^Z convention on purpose any more; many don't even know about it. > >> (Which rises the immediate question why the Microsoft programmers did >> not embed the meta information in this section at the end of the file. >> But i don't really want to know.) > > See above. The intent of ^Z was never to distinguish data from metadata, > as with the Mac data and resource forks. > > But of course none of this has anything to do with U+FEFF. > >> So do the programmers have to face the same conditions? I don't >> really think so. They prefer driving plain text readers up the wall. >> Successfully. > > Again, we don't really have this kind of evil intent, though it's often > fun and convenient for people to imagine we do. > > -- > Doug Ewell | Thornton, Colorado, USA > http://www.ewellic.org | @DougEwell > -- John W Kennedy "Give up vows and dogmas, and fixed things, and you may grow like That. ...you may come to think a blow bad, because it hurts, and not because it humiliates. You may come to think murder wrong, because it is violent, and not because it is unjust." -- G. K. Chesterton. "The Ball and the Cross"
