Unix Components

The UNIX OS consists of the kernel or master control program and the services described above. The kernel controls program start and stop functions, and handles low-level tasks shared by multiple programs, such as file system management.

Most importantly, the kernel schedules hardware access so that programs accessing the same application or device simultaneously do not interfere with each other. The kernel manages a system’s entire resources and represents them coherently to all users. It allocates memory to each process. It transfers data between different parts of the machine. And it interprets and executes shell instructions. However, this model was most effective for linear input and output computing. Modern computing introduced event-driven computing through GUIs. Micro-kernels were developed to perform tasks through smaller utilities and move network protocols outside of the kernel.

After logging into a UNIX system, the user directly interacts through shell programs. Commands are entered at prompts visible on the screen where the cursor is. The shell is the command line interpreter and provides the user interface for UNIX. It identifies the programs to be run and uses file expansion through data streams to connect them to the kernel and each other. Command files or shell scripts are the specific programming languages used to communicate commands to the kernel and return processed results to the display screen.

There are several types of shell scripts that accomplish this function. These include the following: Bourne shell; C shell; Korn shell; TC shell; and Bourne Again shell. However, UNIX allows for programmers to make any program their shell by specifying as much. The Bourne shell is the standard shell for UNIX. Every UNIX or UNIX-like system contains a shell that is compatible with the Bourne shell. UNIX has also developed visual shells like GNOME or KDE to support GUIs.

Utilities provide the primary frontier between user and UNIX. UNIX offers hundreds of utilities, which are also known as ‘commands’. These utilities include universal functions like program support, file maintenance, sorting, editing, printing, and connection to online information. These utilities are modular which can be grouped together through programming to accomplish more complex tasks. As UNIX developed, it also provided for TCP/IP communications utilities for communicating on the Internet.

The focus on text and binaries has also universalized UNIX and disseminated its influence to other UNIX-like systems, like LINUX. The text-based focus has also been popular in application layers of Internet protocols like FTP (File Transfer Protocol), HTTP (Hypertext Transfer Protocol), and XML (Extensible Mark-up Language), which are central to client server technology and any technology that requires communication with the Internet.

Impact / Contributions

As previously stated, UNIX has been instrumental in the movement towards networking. The client-server model is the most common model for interacting with the Internet. Indeed, the Internet itself is a client-server model. This section will examine how UNIX facilitates client-server models, which communicate over the Internet. To understand how UNIX functions as a fundamental component of client-server networking, we will use the popular UNIX-based operating system, LINUX. Like UNIX, LINUX supports TCP/IP as its network transport system. TCP/IP is the basic collection protocols that allow two programs to communicate over a network, regardless of location.

Therefore, it is central to any communication within client-server models, which are organized around network communication. It is one of the underlying technologies that makes the Internet possible. BSD socket interfaces allow network-based applications to be constructed independent of communication facilities. BSD sockets are APIs (Application Program Interfaces) that were developed for UNIX at the University of California at Berkeley. They are also known as Berkley sockets. They function as the standard for network sockets, since most programming languages use C-language APIs, which is also the language of UNIX. However, creating networks through coding in C and using BSD socket APIs can require a lot of labor. Recently, two alternatives have developed, RPC (Remote Procedure Call) and CORBA (Common Object Request Broker Architecture). But UNIX did it first.

Another important innovation by UNIX that influenced the explosion of such profitable web-based industries as e-commerce, was making the command line interpreter a user-level program. The UNIX shell used the same language for interactive commands as it used for scripting. Therefore, new commands could be added to the shell without changing the shell structure. UNIX’s command line syntax provided a model for creating pipelines or chains of producer-consumer processes that form the bulk of e-commerce. E-commerce sites follow client-server models and UNIX is often the backbone of these examples.

UNIX can be used to program both clients and servers. Its natural inclination towards networking with its TCP/IP technology and standard shell lend it to being a foundational operating system for client-server models where computers must network with each other and the Internet to create cost and labor effective environments.

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