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compress (software) facts for kids

Kids Encyclopedia Facts
compress / uncompress
Original author(s) Spencer Thomas
Initial release February 1985; 40 years ago (1985-02)
Operating system Unix, Unix-like, IBM i
Type Command
compress .Z
Filename extension
.Z
Internet media type
application/x-compress
Developed by Spencer Thomas
Type of format data compression

compress is a special computer program for Unix systems. Its main job is to make computer files smaller, which is called data compression. When a file is compressed, it takes up less space on your computer. It can also be sent faster over the internet.

The uncompress program does the opposite. It takes a compressed file and brings it back to its original size. Think of it like packing a big suitcase into a smaller one. Then you unpack it when you need your clothes!

Compared to another popular program called gzip, `compress` is a bit slower at making files smaller. But it's a little faster at making them big again. `gzip` usually makes files even smaller than `compress` does.

How the Programs Work

When you use `compress` on a file, the program usually adds ".Z" to the end of its name. For example, if you compress a file called "report.txt", it might become "report.txt.Z". This helps you know it's a compressed file.

Many programs that handle groups of files, like `tar`, can use `compress`. They can send their data through `compress` to make the whole group of files smaller.

The `uncompress` program can then open these ".Z" files. It restores them to how they were before. It even tries to keep the original date and time the file was created or changed.

A Bit of History

The technology behind `compress` is called the LZW algorithm. It was invented in the early 1980s. A person named Spencer Thomas created the `compress` program in 1984.

However, the LZW algorithm was protected by a patent. A patent is like a special right given to an inventor. It means others have to pay to use their invention. Because of this patent, people had to pay money to use `compress`.

This is why other programs like gzip and bzip2 became more popular. They used different ways to compress files that didn't have patents. These programs also often made files even smaller.

The patent on the LZW algorithm ended in 2003 in the United States. This means anyone can now use the LZW technology without paying. Even though the patent is gone, `gzip` and `bzip2` are still more widely used today. But `compress` is still found on many Unix and BSD computer systems.

Where You Can Find It

The `compress` program was officially standardized in 1994. This means it follows certain rules so it works the same way on different computer systems.

You might not find `compress` installed on every computer by default. Especially on Linux computers, you might need to add it as an extra program. But it is available for many systems like FreeBSD, OpenBSD, and Solaris.

`compress` can also be used for sending information over the internet. For example, it can be used with Point-to-Point Protocol (PPP) or for web pages using HTTP/1.1. However, newer and better compression methods are usually preferred for these uses today.

See also

Kids robot.svg In Spanish: Compress para niños