Showing posts with label Computer System. Show all posts
Showing posts with label Computer System. Show all posts


Types of Operating Systems

           Operating system can be broadly classified into two categories based on the type of interface provided to the user.

Command Line Interface

         In these types of operating systems the user can enter commands through the keyboard and each command will perform a specific action. But this type of interface is very difficult for a beginner to use, because the commands have to be remembered.

          MS-DOS is such a Operating System. Dos stands for Disk Operating system. It was developed by Microsoft as an operating system in the 1980s. Windows 3x needed DOS to run, but the later versions of Windows do not.

Graphical User Interface

         These operating systems provide the user the ability to manipulate the computer in a more interactive way. These systems are more user-friendly and easier to use than command driven interface, because the commands need not be learnt.
E.g. Windows, MacOS, Linux

Windows 7


Operating System

         An Operating System or OS is a software program that enables the computer hardware to communicate and operate with the computer software. Without an Operating System, a computer would be useless.

Features Expected of an Operating System
  • To Startup and Shutdown the computer
  • To act as an interface between the user and the hardware.
  • To perform house keeping tasks such as file handling, disk/ memory management.
  • To be able to allow the user to configure the system. This includes changing the types of printers, adding new hardware (such as sound cards), etc.


System Software


          Software refers to instructions which are used by  the computer to perform various tasks. The word programme is synonymous with software. Software is created with programming languages and related utilities. Software is generally classified into two types: System Software and Application Software.

System Software

          System software is responsible for controlling, integrating and managing the individual hardware components of a computer system so that other software and the users of the system see it as a functional unit without having to be concerned with the low-level details of the computer hardware.
System software can be further classified as:
  • Operating Systems.
  • Utilities and service programs.
Operating Systems (OS)

              The Operating System manages the resources and the basic operations of the computer. Without an operating system the computer would not work. The operating system (or a part of it) is loaded into the main memory when the computer is switched on and handles many tasks, which we are unaware of when we use the computer. A part of the operating system remains in main memory until the computer is turned off.

             There are several operating systems used with personal computers such as Windows 98, Windows XP, Linux and Mac OS. Different systems are designed for different hardware platforms or for different functions.

            Operating systems may provide different types of user interfaces such as Command Line Interface and Graphical User Interface (GUI). In the command line interface, users communicate with the operating system by typing commands using the keyboard. One of the main disadvantages of the command line interface is that the user has to memorize the commands exactly.

               In the graphical user interface, a user invokes a command by means of graphical objects shown on the screen and the system translates the user action to the operating system commands and executes them on behalf of the user. The graphical user interface was first developed for Apple Macintosh Computers.

              The general-purpose operating systems are typically supplied on CD-ROMs and must be installed before using the computer. Some computers such as hand held computers come with pre-installed operating systems on the computers' ROM. Such operating systems provide only limited capabilities and are virtually impossible to be upgraded.

Utilities and Service Programs 

             Another category of software is utility software, which is a collection of useful programs that enhance the capabilities of the operating system. These software programmes are designed to perform various tasks. Some examples of utility software are Norton Utilities and Download Accelerator.


Components of a Computer System

                  By considering the functions performed by various components, a computer can be represented as a collection of logical components as in Figure 1.3. The main hardware components of a modern computer system are the central processing unit (CPU), the main memory, the secondary storage and the In put-Out put devices.

System Unit

                  The system unit, or the cabinet houses most of the essential components of the computer system such as the power supply, the motherboard, the CPU chip, specialized chips, the system clock, RAM, ROM, expansion board and bus lines.

Central Processing Unit (CPU)

The central processing unit performs the majority of calculations and controls the operation of a computer. CPUs are rated by the speed at which they can execute instructions. The speed of a CPU is measured in Megahertz (MHz), and is also known as the clock speed. The higher the value of the speed the faster the computer can run programs. The capacity of a Central Processing Unit is expressed in terms of word size. A word is the maximum number of bits that the CPU can manipulate or store at one time.

The CPU consists of two parts: the control unit (CU) and the arithmetic/logic unit (ALU)

Different manufactures are making CPUs today. Some of these popular CPUs available today are the Intel, AMD, Cyrix and Motorola.

Control Unit (CU)

                  The control unit controls and directs the operation of the entire computer system. Although it does perform any actual processing on the data, the control unit acts as a central nervous system for the other components of the computer. It obtains instructions from the program stored in main memory, interprets the instructions, and issues signals, which cause other units in the system to execute them.

Arithmetic-Logic Unit (ALU)

                  The arithmetic-Logic unit performs arithmetic operations such as addition, subtraction, multiplication and division on data. It also performs logical operations, which involve comparison of data. In microcomputers, the entire CPU is typically fabricated on a single chip.


                  The motherboard is the main circuit board inside the computer. It can be considered as the main communication center through which all the components of the computer transmit data back and forth. All the main parts including the central processing unit of the computer are typically plugged in to the mother board. The mother board also provides sockets, called expansion slots, to plug in special electronic circuitboards to enhance the functionality of the computer. These extra circuitboards are called expansion cards, by using which you can customize a computer to suit your needs. One other major function of the mother board is to supply the necessary power to all its expansion cards.

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