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A system of interconnected computers that share a central storage system and various peripheral devices such as a printers, scanners, or routers. Each computer connected to the system can operate independently, but has the ability to communicate with other external devices and computers.

A computer system is a connection of electromechanical devices that link together forming a system in order to perform automatic electronic data processing (EDP) using software. It can manipulate and store data for the user’s retrieval. It has the capacity to manipulate data to meaningful information. This data can also be stored for later use or further manipulation It is different from other processing machines such as punched cards, calculators etc ., because it can also store instructions that will direct the machine to carry out the steps accordingly. The general perception of people regarding the computer is that it is an ‘intelligent thinking machine’. However, this is not true. Every computer needs to be instructed on exactly what to do and how to do it. The instructions given to the computers are called programs. Without programs, computers would be useless. The physical parts that make up a computer (the central processing unit, input, output and storage unit) are known as hardware. Any hardware device connected to the computer or any part of the computer outside the CPU and the working memory is known as a peripheral; for example, keyboard, mouse and monitor.

 

Components of a Computer System

There are several computer systems in the market with a wide variety of makes, models and peripherals. In general, a computer system comprises the following components:

  • Central Processing Unit (CPU): This unit performs processing of instructions and data inside the computer.
  • Input Unit: This unit accepts instructions and data.
  • Output Unit: This unit communicates the results to the user.
  • Storage Unit: This unit stores temporary and final results.

 

A) Central Processing Unit: The central processing unit, also known as processor, is the brain of the computer system that processes data (input) and converts it into meaningful information (output). It is referred to as the administrative section of the computer system that interprets the data and instructions, coordinates the operations and supervises the instructions. CPU works with data in discrete form, that is, either 1 or 0. It counts, lists, compares and rearranges the binary digits of data in accordance with the detailed program instructions stored within the memory. Eventually, the results of these operations are translated into characters, numbers and symbols that can be understood by the user. Some of the basic functions of a CPU are as follows:

  1. It issues commands to all parts of the computer system.
  2. It controls the sequence of operations as per the stored instructions.
  3. It stores data as well as programs (instruction).
  4. It performs the data-processing operation and sends the results to the output unit.

 

The CPU itself has three parts:

  1. Arithmetic Logic Unit (ALU): This unit performs the arithmetic (add and subtract) and logical operations (and, or) on the available data. Whenever an arithmetic or logical operation is to be performed, the required data are transferred from the memory unit to ALU, the operation is performed, and the result is returned to memory unit. Before the completion of the processing, data may need to be transferred back and forth several times between these two sections.
  2. Control Unit: This unit checks the correctness of the sequence of operations. It fetches the program instructions from the memory unit, interprets them and ensures correct execution of the program. It also controls the input/output devices and directs the overall functioning of the other units of the computer.
  3. Registers: These are the special purpose, high-speed temporary memory units that can hold varied information such as data, instructions, addresses and intermediate results of calculations. Essentially, they hold the information that the CPU is currently working on. Registers can be considered the CPU’s working memory, an additional storage location that provides the advantage of speed.

 

B) Input, Output and Storage Unit: The user must enter instructions and data into the computer system before any operation can be performed on the given data. Similarly, after processing the data, the information must go out from the computer system to the user. For this, every computer system incorporates input and output unit that serve as a communication media between the computer system and the user.

An input unit accepts instructions and data from the user with the help of input devices such as keyboard, mouse, light pen and so on. Since the data and instructions entered through different input devices will be in different forms, the input unit converts them into the form that the computer can understand. After this, the input unit supplies the converted instructions and data to the computer for further processing.

The output unit performs just opposite of that which the input unit does. It accepts the outputs (which are in machine-coded form) produced by the computer, converts them into the user understandable form and supplies the converted results to the user with the help of output devices such as printer, monitor and plotter.

Besides, a computer system incorporates storage unit to store the input entered through input unit before processing starts and to store the results produced by the computer before supplying them ? to the output unit. The storage unit of a computer comprises two types of memory/storage: primary and secondary. The primary memory, also called main memory, is the part of a computer that holds the instructions and data currently being processed by the CPU, the intermediate results produced during the course of calculations and the recently processed data. While the instructions and data remain in main memory, the CPU can access them directly and quickly. However, primary memory is quite expensive and has a limited storage capacity.

Due to limited size of primary memory, a computer employs secondary memory, which is extensively used for storing data and instructions. It supplies the stored information to the other units of the computer as and when required. It is less expensive and has higher storage capacity than the primary memory. Some commonly used secondary storage devices are floppy disks, hard disks and tape drives.

 

Hardware System

The hardware system consists of external and internal physical components that enable a computer to accept input, process the input, store data, and produce outputs. The diagram below shows some external hardware components of a computer.

The diagram below indicates the hardware components inside the system unit. Each of these components plays an essential role in the operation of a computer system.

 

Hardware components provide the physical interface to a computer system. However, they cannot function without instructions to operate them. These instructions are software programs.

 

Software System

Computer software, or just software, is a collection of computer programs and related data that provides the instructions for telling a computer what to do and how to do it. Software is a set of programs, procedures, algorithms and its documentation concerned with the operation of a data processing system.

The two different types of software programs are operating system software and application software.

Operating system software; provides instructions to hardware system components.

Examples of operating systems are the Microsoft Windows operating system and the Macintosh operating system. When an input is entered, the operating system program provides instructions to send the input to appropriate hardware components for processing. Then, it provides instructions for the result to be sent to the appropriate output device. For example, when a user types using a keyboard, the Microsoft Windows operating system takes the input sent through the keyboard and displays the typed letters on the monitor.

 

Application software; provides instructions that enable the user to perform specific tasks such as creating presentations, composing written documents, and editing images. Examples of application software programs are Microsoft Word and Notepad. Application software instructions are handled by the operating system. For instance, when you open a file using Microsoft Word, first the application provides the user-interface for you to specify which file you want to open (for example, the menu bar).

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