UNIX based systems typically of the following components: System Unit, user Terminals, Console, communication lines and Printer (s).
Education of Components of UNIX Based Systems
System Unit: This is that computer, which has the Central processing unit as well as disk for the mass storage. This is that unit which has UNIX Operating System and to which are the other terminals, which used the CPU are connected. This unit acts as a server, serving requests from various terminals.
User terminals: User terminals are those terminals which are connected to the system unit. These are the terminals which enable users to interact with the UNIX system by giving commands and receiving the output on the monitor. These terminals usually have a key board for input and monitor for output. UNIX also supports online terminals, which are directly connected to the Computer System as well as Remote terminals which are connected to the system by using communication lines and moderns.
Console: It is that terminal, which is used to control the system operation. We can even use this unit as any other user terminal to get tasks done by the Operating system.
Communication Lines: These are those cables and lines which are used to connect one system with other systems, so that one can Communicate between the Systems.
Printers: We always need the hard copy of the output, so that we can make use of the output for various purposes. To get this hard copy we need to use printers. UNIX system supports a large range of printers, so that one can get a hard copy. Draft printers, letter printers, Laser Printers etc are supported by UNIX.
UNIX since its development in 1969 has evolved over past thirty years from its initial stages into a very Powerful and Effective Operating System. This credit is bagged by the structure of the UNIX system, which is very robust and its layered structure (which already seen), is very efficient. UNIX is composed of:
Kernel, Shell, Utilities and applications
This breakup of the UNIX makes it very powerful as well as an easy to use operating system. The following figure depicts the Overview of the UNIX Architecture.
Kernel: Kernel can be used as the brain of the UNIX System, which controls the system hardware and performs various low level functions. The kernel is the core of the UNIX system. Kernel is that part of operating system which is the closest to the hardware and it is that which interacts with it directly. Users cannot interact directly with the kernel, they have to use a mediator which is the shell, which interacts with user and gives a via media access to kernel.
Functions of UNIX Kernel
File management and security services, Date and time management, Input-Output handling, Scheduling and management processes, Memory Management, Interrupt and error handling, System accounting, all low level functions.
Whenever the UNIX system has to be ported to other hardware platform, it is that Kernel which has to be customized as per the hardware configuration.
To interact with the Kernel, all the applications, utilities as well as the shell, invoke well structured routines to the Kernel, and these routines are called “System Calls”.
Shell: Shell is the interface between the user and the operating system. It is also the command interpreter of the UNIX. Whenever a user logs into the system, it is that shell, which is started, and it displays a prompt, so that user can start giving commands to the system. It is the shell, which is the interface between the user and the kernel of the UNIX System. Apart from being the interface and command interpreter, it can be treated as a fully fledged programming language, as one can write programs using shell, which are known as “Shell Scripts”.
The shell can be different from system to system, depending on the company which provides the shell. The following are the popular shells which are available.
Bource shell (default with UNIX), ‘C’ Shell, Korn Shell.
These shells have slight variations with respect to the environment and the facilities provided.
UNIX Utilities and Applications
We have already learnt about the utilities and applications which come along with the UNIX Operating System, to support variety of tasks like copying files, calculating, editing, developing applications etc. Some of the UNIX utilities and applications are:
File management programs, text Possessing programs, General System operation, System administration utilities, ‘C’ Programming tools etc.