Magic numbers
This is a number embedded in a file which is used to identify the file type.
Solid archives
A solid archive is one where all of the stored files are compressed in a single operation. A zip file is
typically not a solid file because the files are compressed individually.
Advantages...
- Much better compression is achieved.
Disadvantages...
- Slower access, the whole archive must be decompressed in order to retrieve a singe file.
- A single error will make all the files in the archive unrecoverable.
The archive file's type is identified by looking at it's magic number, not at it's extension.
The following types will be correctly identified...
- Zip
- GZip
- Tar
- BZip2
- GZip files containing a Tar archive.
- GZip files containing a Zip archive.
- BZip2 files containing a Tar archive.
- BZip2 files containing a Zip archive.
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