Zip

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Draft

1 Introduction

This article provides a short description of the ZIP file format.

Zip files have two purposes:

  1. Pack several files (including directory structures) into a single archive file.
  2. Compress these files. Compression is optional and usually automatically done with "deflate"

“Zip files are archives that store multiple files. Zip allows contained files to be compressed using many different methods, as well as simply storing a file without compressing it. Each file is stored separately, allowing different files in the same archive to be compressed using different methods. Because the files in a Zip archive are compressed individually it is possible to extract them, or add new ones, without applying compression or decompression to the entire archive. This contrasts with the format of compressed tar files, for which such random-access processing is not easily possible.” (Wikipedia, March 2013)

2 Tips

  • You cannot execute software that sits in a zip archive. Uncompress first (that mostly concerns Windows users: watch out for a "zip" icon)
  • Typically software (e.g. a web browser) cannot directly read a file from a zip archive
  • *.docx and CS6 *.fla files are zip archives
  • *.jar files are a variant.
  • There are several zip version. In particular, there is a recent *.zipx version which cannot be opened with all software since it includes a greater variety of compression algorithms

3 Tools

Compression/uncompression

Many tools can handle several types of archives, e.g, 7z and tar/targz, see Wikipedia's Comparison of file archivers for a good list.

  • More recent Win, MacOSX and Linux systems provide simple built-in tools. On Windows, we suggest installing additional software that will provide more fine-grained control.
  • 7-Zip (Windows) is a popular recommended program at the time of writing.
Repair

4 Links

  • ZIP (Wikipedia)