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Unix

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Unix is a family of multitasking and multi-user computer operating systems. An operating system is the essential software that manages a computer's hardware and software resources.

Ken Thompson and Dennis Ritchie
Ken Thompson and Dennis Ritchie

Unix is highly significant because it introduced portability to the computing world. This means the system can be moved and run on many different types of computer hardware. It provides a foundation for many modern technologies, from massive supercomputers to the software in mobile devices. Its design principles continue to influence how programmers write and organize software today.

The core of a Unix system is the kernel. The kernel is a master control program that provides essential services to all other programs. It handles the file system and manages how memory is used. The kernel also performs process scheduling, which means it decides which program gets to use the computer's processor at any given moment. To prevent different programs from crashing into each other, the kernel manages access to shared resources. It maintains a distinction between kernel space, where these high-level tasks happen, and user space, where most regular application programs operate.

Version 7 Unix SIMH PDP11 Emulation DMR
Version 7 Unix SIMH PDP11 Emulation DMR

Unix is defined by a specific approach called the "Unix philosophy." Rather than building one massive, complex program to do everything, Unix provides a collection of small, simple tools. Each tool is designed to perform a single, well-defined function. These tools can be linked together to perform much larger and more complex tasks. This is achieved through a mechanism called "pipes," which allows the output of one program to serve as the input for another.

Usenix84 1
Usenix84 1

This modular design is supported by a hierarchical, inode-based filesystem and a command-line interpreter known as a shell. The shell allows users to combine these small tools into powerful workflows through shell scripting.

The history of Unix began in the mid-1960s during the development of a complex system called Multics. Researchers at Bell Labs, including Ken Thompson and Dennis Ritchie, became frustrated with the size and complexity of Multics. They decided to create a smaller, more manageable project. Initially, the system was single-tasking and lacked an official name. In 1970, the group coined the name "Unics" as a pun on Multics, which eventually became the spelling "Unix."

UNIX-Licence-Plate
UNIX-Licence-Plate

Early versions ran on machines like the PDP-7 and PDP-11 using assembly language.

A major turning point occurred in 1973 when Version 4 Unix was rewritten in the C programming language. This was a massive technical achievement because it allowed Unix to become portable across different computer platforms. Before this, most operating systems were tied to specific hardware. This change allowed Unix to spread rapidly through academic and commercial circles. By the late 1970s, Bell Labs was licensing Unix to outside parties. This led to the creation of many different versions, such as BSD from the University of California, Berkeley, and Xenix from Microsoft.

HP-HP9000-C110-Workstation 10
HP-HP9000-C110-Workstation 10

As Unix spread, the industry entered a period known as the "Unix wars," where different vendors created competing versions. These versions, such as SunOS, AIX, and HP-UX, were often incompatible with one another. To solve this, AT&T and Sun Microsystems worked to merge several versions into UNIX System V Release 4 (SVR4) in 1989. This helped standardize many of the system's features. Today, the UNIX trademark is managed by The Open Group. They ensure that certified operating systems comply with the Single UNIX Specification (SUS). This standardization allows different systems to maintain a level of compatibility.

The impact of Unix on modern computing is immense. Until 2005, it was the most widely used operating system for servers. Even now, distributions like IBM AIX and Oracle Solaris are used in specialized fields. In the 1990s, Unix-like systems became the standard for over 90% of the world's 500 fastest supercomputers. Furthermore, the Unix environment was essential for developing the Internet and the client-server model. Even the macOS operating system used by many people today is built upon a Unix core called Darwin.

CDE 2012 on Linux
CDE 2012 on Linux

From the servers that power the web to the phones in our pockets, the legacy of Unix is everywhere.

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🖼️ Images & Media (6)
File:Version 7 Unix SIMH PDP11 Emulation DMR.png
Version 7 Unix SIMH PDP11 Emulation DMR.png
File:CDE 2012 on Linux.png
CDE 2012 on Linux.png
File:Ken Thompson and Dennis Ritchie.jpg
Ken Thompson and Dennis Ritchie.jpg
File:Usenix84 1.jpg
Usenix84 1.jpg
File:UNIX-Licence-Plate.JPG
UNIX-Licence-Plate.JPG
File:HP-HP9000-C110-Workstation 10.jpg
HP-HP9000-C110-Workstation 10.jpg
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