A parameter is an entity that stores values. It can be a name, a number, or one of the special characters listed below. For the shell's purposes, a variable is a parameter denoted by a name.

 Memory management subsystem implements the virtual memory concept and a user need not worry about the executable program size and the RAM size.

There are many systems which are Unix-like in their architecture .

A Unix kernel — the core or key components of the operating system — consists of many kernel subsystems like process management, memory management, file management, device management and network management.

A fundamental simplifying assumption of Unix was its focus on ASCII text for nearly all file formats. There were no "binary" editors in the original version of Unix – the entire system was configured using textual shell command scripts. The common denominator in the I/O system was the byte – unlike "record-based" file systems.

Unix was the first operating system to include all of its documentation online in machine-readable form .

man – manual pages for each command, library component, system call, header file, etc

Commands – Unix makes little distinction between commands (user-level programs) for system operation and maintenance commands of general utility , and more general-purpose applications such as the text formatting and typesetting package.

Unix provided the TCP/IP networking protocol on relatively inexpensive computers, which contributed to the Internet explosion of worldwide real-time connectivity, and which formed the basis for implementations on many other platforms. This also exposed numerous security holes in the networking implementations

It was written in high level language rather than assembly language (which had been thought necessary for systems implementation on early computers). Although this followed the lead of Multics and Burroughs, it was Unix that popularized the idea.

The Unix system is composed of several components that are normally packed together. By including – in addition to the kernel of an operating system – the development environment, libraries, documents, and the portable, modifiable source-code for all of these components, Unix was a self-contained software system. This was one of the key reasons it emerged as an important teaching and learning tool and has had such a broad influence

Unix operating systems are widely used in servers, workstations, and mobile devices.^[2] The Unix environment and the client–server program model were essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers.
Both Unix and the C programming language were developed by AT&T and distributed to government and academic institutions, which led to both being ported to a wider variety of machine families than any other operating system. As a result, Unix became synonymous with "open systems".

Unix

Unix is open source operating system .