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| Filename 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, and for a time with the Commodore Amiga community.
Technical Specification
A .ZOO archive begins with a 34-byte header field, as follows
| Decimal Offset |
Hex Offset |
Size in Bytes |
Description |
|---|---|---|---|
| 000-019 | 000-013 |
|
Archive header text, padded with nulls, terminated by ^Z |
| 020-023 | 014-017 |
|
Hex string DCA7C4FD |
| 024-027 | 018-01B |
|
Offset of first file in archive |
| 028-031 | 01C-01F |
|
0xFFFFFFFF - Offset of first file in archive |
| 032 | 020 |
|
Minimum version of ZOO needed to extract files from archive (major part) |
| 033 | 021 |
|
Minimum version of ZOO needed to extract files from archive (minor part) |
Newer ZOO files, from version 2.00, can contain an extended archive header field, beyond the original 34 bytes. The existence of this extended archive header can be detected by looking at the offset of the first file in the archive.
| Decimal Offset |
Hex Offset |
Size in Bytes |
Description |
|---|---|---|---|
| 034 | 022 |
|
Archive header type; 1 for now |
| 035-038 | 023-026 |
|
Offset of archive comment |
| 039-040 | 027-028 |
|
Size of archive comment |
| 041 | 029 |
|
Generation limit, for handling multiple file generations |
Each stored file has its own header, which looks like this
| Decimal Offset |
Hex Offset |
Size in Bytes |
Description |
|---|---|---|---|
| 000-003 | 000-003 |
|
Hex string DCA7C4FD |
| 004 | 004 |
|
Type of directory entry: 0 - Old header format; 1 - Extended header format |
| 005 | 005 |
|
Compression method: 0 - Stored without compression; 1 - Crunched (LZW); 2 - LZH (Requires ZOO 2.10) |
| 006-009 | 006-009 |
|
Offset of next directory entry |
| 010-013 | 00A-00D |
|
Offset of file data |
| 014-015 | 00E-00F |
|
Original date of file in MS-DOS format |
| 016-017 | 010-011 |
|
Original time of file in MS-DOS format |
| 018-019 | 012-013 |
|
CRC-16 of file |
| 020-023 | 014-017 |
|
Uncompressed file size |
| 024-027 | 018-01B |
|
Compressed file size |
| 028 | 01C |
|
Minimum version of ZOO needed to extract this file (Major part) |
| 029 | 01D |
|
Minimum version of ZOO needed to extract this file (Minor part) |
| 030 | 01E |
|
Deleted flag: 0 - File is present; 1 - file is marked as deleted |
| 031 | 01F |
|
Structured file?? |
| 032-035 | 020-023 |
|
Offset to file comment field or 0 if no comment |
| 036-037 | 024-025 |
|
Length of comment field |
| 038+ | 026+ | Variable | File name, which may include a path, null terminated |
Other uses
The file format .zoo are also saved zoos for Microsoft's Zoo Tycoon PC game.
External links
- zoo 2.10 source
- unzoo - zoo archive extractor, source included
