🚀 go-pugleaf

In article <8609170125.AA12047@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes:
>
>>jimb@amdcad.UUCP (Jim Budler)  Writes:
>>Normal file system? Did you ever notice that in unix applications there
>>are two 'forks' called text and data.  The difference is that the
>>address of the two 'forks' is contained in the file itself, and on the mac
>>the addresses are in the directory.
>
>	What are you talking about?
>
>			-Matt



Try the command `size /bin/*sh' sometime. This will display something like:
text	data	bss	dec	hex
65536	2048	19836	87420	1557c	/bin/csh
18432	3072	16844	38348	95cc	/bin/sh
The command `ls -l /bin/sh' gives:
-rwxr-xr-x  1 root        68608 Jul 10  1983 /bin/csh
-rwxr-xr-x  1 root        22528 Jul 10  1983 /bin/sh

As you'll note, text + data is approx. file size.
bss is `buffered storage space'.  This is preallocated space. The program
will take a minimum of text + data + bss memory to run (although paging
on a vmunix system can allow programs totaling more than physical
memory, echh!)

My point is that Unix systems store the file with one directory entry,
then within an application, the first portion of the file ( the a.out
header) defines where the text and data portions begin. On a mac
there are two directory entries, one for the data fork, one for the
resource fork.

The application `size' gets the information above from the file, using the
structure defined in <a.out.h> or <nlist.h> (depending on your version of
UNIX). Diskinfo, on a Mac, gets the some of the same information from the
directory.

The Mac extended the concept a bit by having the two sections (forks)
for non-applications.

Is one or the other `normal'?
Is one or the other `antiquated'?
Is one or the other `better'?
Is one or the other `newer'?

The adjective `normal' as applied to the Unix file structure was what I
was trying to oppose. I was not trying to say that they were exactly similar.

The advantage of the Unix system?
	A simpler directory structure? I doubt it. The Unix directory
	structure is far more complex than the Macintosh directory
	structure. It contains a pointer to the inode describing the physical
	location of the beginning of the file. It contains information about
	modification date of the file, access date of the file, and size
	of the file. The inode structure is the real heart of the Unix file
	structure, and nothing the Mac has approaches it.

The advantage of the Macintosh system?
	The directory structure contains two things the Unix structure does not:
		The creation date of a file.
		The starting address of TWO sections. Roughly, and I mean
		roughly, equivalent to the text and data segments of a Unix
		application. 
	It lacks:
		The inode structure, which can tell you when a particular
		physical segment of a file is modified (I believe dump
		uses this rather than the directory entry to determine
		what needs to be backed up). File tags on a Mac don't
		approach this, especially since they are relatively
		unsupported.

	It gains:
		The ability to modify one portion of the file (i.e. Redit and
		Resedit) without disturbing the other. You cannot expand
		any portion of a Unix application without recompiling. With
		`adb'(sdb,dbx) you can shorten some things (strings) and modify
		others, but not expand, without recompiling.

		The creation date. The finder copies a file, maintaining this
		date. The newer versions of binhex and related terminal
		programs maintain this date. It is useful. 

As to the actual comparison between the Unix text+data and Mac rsrc+data?

	Depends on the programmer.
		If he programs entirely Unix style, all information
		in the code, no resources, then his CODE resource is
		equal to Unix text + data. And his resource fork
		may contain nothing but CODE ID=0 and CODE ID=1.
		His data fork will be empty.

		If he programs Mac style, with resources, then his
		CODE resources are approx. equal to Unix text + part of
		the data, and the rest of the resources + the data fork
		may equal the rest of the Unix data. Most Mac applications
		do not use their own data fork, but some store static data
		there. Unix applications store all of their static data
		in their data segment.

I think a comparison should be on the merits, not on the appearance,
and certainly not on the state of `normallcy'.

I'm certain I will receive much mail/posting/flames telling me how wrong
my view of file structures, both Mac and Unix, are. I welcome mail
and corrective information. Flames I can do without.
-- 
 Jim Budler                                   X   X
 Advanced Micro Devices, Inc.                  X X
 (408) 749-5806                                 X
 Usenet: {ucbvax,decwrl,ihnp4}!amdcad!jimb     X X
 Compuserve:	72415,1200                    X   X

Signature, what signature? I'll make my mark!!