noaguile@ndsuvax.UUCP (07/19/86)
Hello, is it possible to read just 1 bit from the disk drive? how? I would
appreciate any help.
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hsu@eneevax.UUCP (Dave Hsu) (07/22/86)
In article <237@ndsuvax.UUCP> noaguile@ndsuvax.UUCP (Valdir Aguilera) writes: > > Hello, is it possible to read just 1 bit from the disk drive? how? I would >appreciate any help. Huh? Just what are you trying to do? -dave -- David Hsu (301) 454-1433 || -8798 "It was Dave, not me..honest!" -eneevax Communication & Signal Processing Lab / Engineering Computer Facility The University of Maryland -~- College Park, MD 20742 ARPA:hsu@eneevax.umd.edu UUCP:[seismo,allegra,rlgvax]!umcp-cs!eneevax!hsu "Get back in the cupboard, you pantomimetic regal person..."
heins@isucs1.UUCP (07/23/86)
To read just one bit, you'll have to read a whole sector (using DOS 3.3)
or a whole block (using ProDOS), and then extract the byte which contains
the bit you're looking for, and then use AND with the right mask to
mask out the other 7 bits in the byte, and a CMP to tell if its on or
off... or you could look in either "Beneath Apple DOS", or "Beneath
Apple ProDOS" both are by Peter Lechner and Don Worth and published by
Quality software. They detail the inner workings of their respective
DOSes, including GCR, and how bits are written and read from the disk.
Lee Heins
{umn-cs, okstate, csu-cs}!isucs1!heins
heins@iowa-state.CSNET
Note: I have no affiliation with Quality software except that I am a
satisfied owner of both of the books mentioned.
Disclaimer: My opinions are in no way the official opinions of Iowa State
University, and any resemblance thereof is purely coincidental...