A document found on the internet describing the basics of the
Apple Pascal disk format.
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Robert Greene
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Date: Tue, 10 Dec 2002 02:54:19 GMT
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Server: NCSA/1.5.1
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Last-modified: Sun, 18 Jan 1998 23:41:02 GMT
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Content-type: text/plain
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Content-length: 4381
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Path: news1.icaen!news.uiowa.edu!news1.chicago.iagnet.net!iagnet.net!128.223.220.30!logbridge.uoregon.edu!news.uoregon.edu!!nparker
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From: nparker@inferno.uoregon.edu (Neil Parker)
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Newsgroups: comp.sys.apple2.programmer
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Subject: Re: Q: Pascal file system?
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Date: 18 Jan 1998 11:58:17 GMT
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Organization: Chaos
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Lines: 96
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Message-ID: <69sqop$mpu$1@pith.uoregon.edu>
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References: <69sl3k$6sv$1@elna.ethz.ch>
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NNTP-Posting-Host: ssil.uoregon.edu
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X-Trace: pith.uoregon.edu 885124697 23358 nparker 128.223.108.115
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X-Complaints-To: usenet@news.uoregon.edu
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Originator: nparker@
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Xref: news1.icaen comp.sys.apple2.programmer:9640
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In article <69sl3k$6sv$1@elna.ethz.ch>,
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Henrik 'Ratte' Gudat <GUDATH@EZINFO.VMSMAIL.ETHZ.CH> wrote:
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>Hi there,
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>
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>I'm currently looking for a few infos on the Pascal disk format. Anyone knows
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>the specs off hand?
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>
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>Like..
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>- does the Pascal system work with 3.5" media and hard disks?
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Yes and no. Version 1.3 works with 3.5-inch disks. Version 1.1 doesn't
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(unless you patch it). I don't think either version will use a Pascal
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partition on a hard disk, except that there was a program called Pascal
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Profile Manager that could put a Pascal volume into a specially-formatted
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file on a ProDOS-formatted Profile hard disk (I don't think it recognized
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any hard disk other than a Profile).
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(This, by the way, is the reason why ProDOS has storage type 4 (Pascal
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area) and file type $EF (PAS). See ProDOS Technical Note #25,
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"Non-Standard Storage Types".)
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>- has a Pascal disk the same track/sector layout as a ProDOS disk?
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Yes.
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And in case you're interested, here's the Pascal disk layout:
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Blocks 0 and 1 are the boot blocks. The directory occupies blocks 2
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through 5. It contains 78 entries, each 26 bytes long. Block boundaries
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are ignored--the entire directory is treated as a single contiguous
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2048-byte array.
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The first entry is the volume name. It has the following format:
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+0 word: block number of 1st directory block (always 0)
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+2 word: block number of last directory block +1 (always 6)
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+4 word: entry type (0=volume header)
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+6 string[7]: volume name (with length byte)
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+14 word: number of blocks on disk
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+16 word: number of files on disk
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+18 word: last access time
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+20 word: most recent date setting
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+22 4 bytes: reserved
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The remaining entries are file entries:
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+0 word: block number of file's 1st block
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+2 word: block number of file's last block +1
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+4 word: bits 0-3: file type
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1=xdskfile (for bad blocks)
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2=codefile
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3=textfile
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4=infofile
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5=datafile
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6=graffile
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7=fotofile
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8=securedir (whatever that means)
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bits 4-14: reserved
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bit 15: used by Filer for wildcards
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+6 string[15]: file name (with length byte)
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+22 word: number of bytes used in file's last block
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+24 word: file modification date
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The last 20 bytes of the directory are unused.
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The date setting and last modification date are stored in a word as
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follows:
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Bits 0-3: month (1-12)
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Bits 4-8: day (1-31)
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Bits 9-15: year (0-99)
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When you find an entry whose name is the null string, you've reached the
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end of the directory. There are no special "deleted file" entries--when a
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file is deleted, it is "squeezed out" of the directory by moving the
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following entries one slot forward.
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Files are stored contiguously on the disk...that is, each file occupies
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all the blocks starting at the first block number listed in its directory
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entry, and ending at one less than the last block number listed in its
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directory entry. Directory entries are sorted in order of increasing block
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number. There is no block map--due to the contiguous allocation scheme,
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free space can easily be located by scanning the directory: if a
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directory entry's last-block-number field doesn't match the next entry's
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first-block-number field, then you've found some free space.
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All "word" entries are, of course, stored in standard Apple II
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low-byte-first order.
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- Neil Parker
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--
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Neil Parker, nparker@inferno.uoregon.edu, nparker@axis.llx.com,
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http://axis.llx.com/~nparker/ (Note new addresses and home page!)
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Unsolicited commerical e-mail is not welcome, and will be discarded unread.
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