06.013 What file types does DOS 3.3 have and how is file type information saved in the Catalog?
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
06.013 What file types does DOS 3.3 have and how is file type information saved in the Catalog?
In a DOS 3.3 Catalog sector, the third byte in each file's entry tells the
type of the file:
Byte Value* File Type
00 Text
01 Integer BASIC
02 AppleSoft BASIC
04 Binary
08 S type
10 R: Relocatable object module
20 new A type
40 new B type
*DOS 3.3 sets bit 7 of the byte if the file is locked. (e.g. 84 --> a locked
Binary file)
Type R files show up in just a few applications. An R file begins with 6
bytes which a "loader" routine can use to tell the Target location of file
contents, How many bytes to move, and Source location to move from.
Although S, new A, and new B are included, no official application was
defined for them and no DOS commands were created to make any special use of
these files.
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from David Empson
There was an "R" type relocating loader included with the toolkit for use
with BASIC programs and relocatable routines being loaded into upper memory.
"S" was used by some programs for a generic image file, or something that
was not likely to be touchable with normal code.
The LISA assembler used the second "B" type for its source files. It had a
patched version of DOS that changed the file type list to read "LARSBAIT", so
the source files appeared in the catalog as "L" if you booted LISA, or "B" if
you booted a normal disk.
The "B", "A", "R" and "S" special file types cannot be accessed by BASIC
programs (unless you patch DOS) - commands are only provided for dealing with
"B", "A", "I" and "T" files.
The four special types can only be accessed using direct calls to the File
Manager.
___________________________
By: Dave Althoff, Jr.
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