Unix Facts for Kids

Quick facts for kids
Unix

Unix System III running on a PDP-11 simulator
Company / developer	Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna at Bell Labs
Programmed in	C and assembly language
OS family	Unix
Source model	Historically proprietary software, while some Unix projects (including BSD family and illumos) are open-source
Initial release	Development started in 1969 First manual published internally in November 1971 (1971-11) Announced outside Bell Labs in October 1973 (1973-10)
Available language(s)	English
Kernel type	Varies; monolithic, microkernel, hybrid
Influenced by	CTSS, Multics
Default user interface	Command-line interface and Graphical (Wayland and X Window System; Android SurfaceFlinger; macOS Quartz)
License	Varies; some versions are proprietary, others are free/open-source software

A timeline showing the history of Unix and its different versions.

Unix is a special kind of computer program called an operating system. Think of it as the main brain that helps your computer run everything. It was first made in 1969 at a place called Bell Labs.

Smart people like Ken Thompson, Dennis Ritchie, Douglas McIlroy, and others created it. They first wrote it using a basic computer language called assembly language. Later, in 1972, they rewrote Unix using a newer, more powerful language called C.

Unix is a multiuser and multiprocessing system. This means many people can use the same computer at once. It also means the computer can run several programs at the same time. Unix works well when computers are connected in a network. Keeping the computer safe from unwanted access is also important in Unix. This is because many people can use it, either directly or over a network.

Many new ideas in Unix were later copied by other operating systems. Because of this, people sometimes talk about a "Unix philosophy." This means a certain way of designing computer systems. Linux is an example of a system that uses many Unix ideas. However, Linux does not use the exact code from Unix. It only shares some ideas and command names. So, Linux is not a true Unix system; it's called "Unix-like."

In Unix and Unix-like systems, many different users can have their own space. This personal area is called a user account. It's where you keep your files and settings.

One way to use a Unix system is with the command line interface. Users type text commands to run programs. This can take time to learn. But it is a very powerful and flexible way to work. Many computer experts still use it. These commands are typed into a "shell," which can be a bit different on various systems.

Another way to use Unix is with a graphical user interface (GUI). This is what most people are used to. The X Window System is a common GUI for Unix systems. The X Window System helps display things on your screen. But it doesn't let you move or resize windows by itself. For that, you need a special program called a window manager or desktop manager.

Some popular desktop managers for Unix-like systems are:

These GUIs use windows, pop-up boxes, and a computer mouse. They are made to be easy to use. There are thousands of programs for the X Window System. These include word processors and spreadsheets. Many of them are open-source software, meaning they are free to use and change.

Types of Unix Systems
How Unix Started
Images for kids
See also

Types of Unix Systems

Today, there are two main kinds of operating systems that are like Unix.

The first group includes systems that share some of their core code with the original Unix. These are often commercial versions like Solaris or AIX.

The second group includes free operating systems. Many of these have "BSD" in their name. Examples are FreeBSD, OpenBSD, and NetBSD. These are based on a free version of Unix called BSD. Even Mac OS X is based on BSD.

There are also free systems based on the Linux kernel. These do not share any code with the original Unix. BSD systems share very little code with the original Unix now. This is because much of their code has been rewritten over many years. To be clear, many people use the terms Unix and Unix-like systems.

Most computer programs can run on any modern Unix or Unix-like system. Programs like KDE and GNOME were first made for Linux. Later, they were changed to work on other types of Unix systems too.

How Unix Started

The story of Unix goes back to the mid-1960s. At that time, the Massachusetts Institute of Technology, Bell Labs, and General Electric were working on a big project. They were creating an operating system called Multics. It was designed for a large computer called the GE 645. Multics was a "time-sharing" system. This meant many users could share the computer's power at the same time.

Multics had many new ideas, but it was also very big and complicated. Some researchers at Bell Labs, like Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna, left the Multics project. They decided to create a smaller, simpler operating system based on what they learned. This new system started without a name or official support.

At first, the new operating system could only do one task at a time. In 1970, the group came up with the name Unics. This was a playful name, a "pun" on Multics. Unics stood for Uniplexed Information and Computing Service. Brian Kernighan is often given credit for the idea. But no one can quite remember how the final spelling Unix came about.

The operating system was first written in assembly language. But in 1973, Version 4 Unix was rewritten in the C language. This made it easier to move Unix to different types of computers. The first time Unix was moved to a different computer was in 1977. This was Version 6, moved to an Interdata 7/32 computer.

Bell Labs made several versions of Unix. These are known as Research Unix. In 1975, the first license to use the UNIX code was sold to a university.

In the late 1970s and early 1980s, Unix became very popular in schools and universities. This led to many companies starting to use Unix. But this also caused Unix to split into many similar versions. These versions were often slightly different and didn't always work together perfectly. Some examples include DYNIX, HP-UX, SunOS/Solaris, AIX, and Xenix. In the late 1980s, a new version called System V Release 4 (SVR4) was created. Many commercial Unix companies then started using it.

In the 1990s, Unix and Unix-like systems became even more popular. They became the top choice for over 90% of the world's fastest supercomputers. This was thanks to BSD and Linux versions. These were developed by many programmers working together around the world. In 2000, Apple released Darwin. This was also a Unix system. It became the core of the Mac OS X operating system, which is now called macOS.

Today, Unix-like operating systems are widely used. You can find them in modern servers, powerful workstations, and even mobile devices like smartphones.