Zoo (file format)

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zoo
File extension: .zoo
Type of format: data compression

zoo is a compression program and format developed by Rahul Dhesi in the mid 1980s. The format is based on the LZW compression algorithm and compressed files are identified by the .zoo file extension. It is no longer widely used. Program source code was originally published on the comp.sources.misc Usenet newsgroup, and was compatible with a variety of Unix-like operating systems. Binaries were also published for the MS-DOS user community. A small companion program was also developed, entitled booz, that provides only decompression functionality.

The .ZOO file format was mostly popular with Digital (now Hewlett Packard) VAX computers running the OpenVMS operating system.

A .ZOO archive begins with a 34-byte header field, as follows
Decimal
Offset		 Hex
Offset		 Size
in Bytes		 Description
000-019 000-013
20
 Archive header text, padded with nulls, terminated by ^Z
020-023 014-017
4
 Hex string A7DCFDC4
024-027 018-01B
4
 Offset of first file in archive
028-031 01C-019
4
 Offset of first file in archive - 1
032 020
1
 Version of ZOO this Archive was created by
033 021
1
 Minimum Version of ZOO needed to extract files from archive


Each stored file has its own header, which looks like this
Decimal
Offset		 Hex
Offset		 Size
in Bytes		 Description
000-003 000-003
4
 Hex string A7DCFDC4
004 004
1
 Type of directory entry
005 005
1
 Compression method; 0 - Stored without compression; 1- Crunched (LZW)
006-009 006-009
4
 Offset of next directory entry
010-013 00A-00C
4
 Offset of next header
014-016 00D-011
2
 Original date and time of file
017-018 012-013
2
 CRC-16 of file
019-022 014-017
4
 Uncompressed file size
023-026 018-01B
4
 Compressed file size
027 01C
1
 Version of ZOO by which this file was compressed
028 01D
1
 Minimum version of ZOO needed to extract this file
029 01E
1
 Deleted flag: 0-File is present; 1-file is marked as deleted
030 01F-022
4
 Offset to file comment field or 0 if no comment
031-032 023-024
2
 Length of comment field
033+ 025+ Variable File name, which may include a path, null terminated

The file format .zoo are also saved zoos for Microsoft's Zoo Tycoon PC game.

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