Computer Hardware and Network

  Computer Hardware and Network

1.	Introduction of Hardware and Software/components of computer.

Unit 1: Introduction to Hardware and Software

CONTENTS

Introduction

Objectives

Computer Hardware

Central Processing Unit

Input Devices

Output Devices

Storage Devices

Network System

Types of Networks

Computer Software

System Software

Application Software

Summary

Keywords

Review Questions

Further Readings

Objectives

After studying this unit, you will be able to:
l    Explain the concept of Computer Hardware
l    Discuss the Input and Output Devices
l    Describe network system
l    Explain the concept of Computer Software

A computer is a combination of two terms Hardware and Software. The physical components of a computer are called hardware. Pieces of hardware may be categorized according to the functions each performs:

 input, process, output, and storage. Your PC (Personal Computer) is a system, consisting of many components. Some of those components, like Windows XP, and all your other programs, are software. Software is the source of interaction between the user and the computer. It represents programs, collection of several sets of instructions, which allow the hardware to run properly. The stuff you can actually see and touch, and would likely break if you threw it out a fifth-story window, is hardware

CComputer Hardware

Hardware of a computer is made up of complex electronic circuits. For a user the details of the circuitry are not important. However, the hardware units with which a user has to interact must

be clearly understood. For convenience, the hardware of a computer
 can be classified in the following categories: 

Input Devices

Output Devices

Central Processing Unit (CPU)

Memory or Storage

Motherboard

Let us discuss each of these hardware components:

1.            Input Devices: The form in which data is available to a user is not always in the same form as is accepted by computer hardware. Input devices are hardware equipment that receive data and instructions from users, convert the data and instructions into a form that can be processed by the computer and passes the same to the computer. Hence, if you have to enter employees’ names into the computer you do not have to write it on a piece of paper and shove the paper inside the computer. You will need some input device for this.

Example: A keyboard is an example of input device.

2.            Output Devices: The result, produced by a computer after processing, is not always in user readable form. An output device is hardware equipment that translates this non-readable result into a form understood by the users.

Example: A VDU (Visual Display Unit) or monitor is an example of output device.

3.     Central Processing Unit (CPU): Central processing unit is to computer what brain is to our body. It is the master organ of a computer. No computer can exist without a CPU. It is composed of two simpler hardware units - Arithmetic Logic Unit (ALU) and Control Unit (CU). CU controls all the activities of other hardware units while ALU performs all the calculations. Computer CPUs are very fast in their calculations and swift in control.

4.      Memory or Storage: This hardware is the place where a computer stores all the data and instructions given to it. The results of the processing are also stored here. A computer has many types of memories. Some memories are directly connected to the CPU and are extremely fast as far as storage and retrieval of data is concerned. These memories are called primary memory - RAM (Random Access Memories) and ROM (Read Only Memories) belong to this

category of memories. The CPU takes data and instructions stored only in the primary memories.

Notes Primary memories are also of varioustypes. The one that looses its contentswhen power is switched off is known as volatilememory such as RAM. Some memories retain the data and instructions stored on them even afterthe power is switched off such as ROM. These memories are known as non-volatile memories.

Secondary storage devices are placed outside the system unit and can be carried from one system to another allowing portability of data and instructions. Floppy disks ordiskettes, hard disks and CD-ROM are some of the secondary storage devices. Input devices, output devices and secondary storage devicesare not directlyconnected to the CPU and hence are known as peripheral devices or simply peripherals.

5.     Motherboard: Motherboard, also called as System Board, is the most important hardware component of a microcomputer. Motherboard is so called as all the other boards (printed circuit boards having chips or other electronic components) of the computer are connected to this board, hence it is like the mother of all other boards.

Now we will discuss the components of computer hardwarein detail.

                  Central Processing Unit

Central Processing Unit (CPU) is the main component or “brain” of a computer,which performs all the processing of input data. Its functionis to fetch, examine and then executethe instructions stored in the main memory of a computer.In microcomputers, the CPU is built on a single chip orIntegerated Circuit (IC) and is called as a Microprocessor. The part of a computer (a microprocessor chip) that does most of the data processing, the CPU and the memory form the central part of a computer to which the peripherals are attached. The Central ProcessingUnit (CPU) is the part of a computerthat interprets and carries out the instructions contained in the software.

The CPU consists of the followingdistinct parts:

l    Arithmetic Logic Unit (ALU): The arithmetic and logic unit of CPU is responsible for all arithmetic operations like addition, subtraction, multiplication and division as well as logicaloperations such as less than, equal to and greater than. Actually,all calculations and comparisons are performed in the arithmeticlogic unit.

l    Control Unit (CU): The control unit is responsible for controlling the transfer of data and instructions among other units of a computer. It is considered as the “CentralNervous System” of computer,as it managesand coordinates all the units of the computer.It obtains the instructions from the memory, interprets them and directs the operation of the computer. It also performs the physical data transfer between memory and the peripheral device.

l    Registers: Registers are small high speed circuits(memory locations) which are used to storedata, instructions and memory addresses (memory location numbers), when ALU performs arithmetic and logical operations. Registers can store one word of data (1 word = 2 bytes & 1 byte = 8 bits.) until it is overwritten by another word. Depending on the processor’s capability, the number and type of registers vary from one CPU to another. Registers can be dividedinto six categories viz. General Purpose Registers, Pointer Registers, Segment Registers, Index Registers, Flags Register and Instruction Pointer Register,depending upon theirfunctions. The detailedfunctions of each and everyregister is beyond the scope of this book.

l    Buses: Data is stored as a unit of eight bits (BIT stands for Binary Digit i.e. 0 or 1) in a register. Each bit is transferred from one registerto another by means of a separatewire. This group of eight wires, which is used as a common way to transferdata between registers is known as a bus. In general terms, bus is a connection between two components to transmit signal between them. Bus can be of three major types viz. Data Bus, Control Bus and Address Bus. The data bus is used to move data, address bus to move address or memory location and control bus to send control signalsbetween various components of a computer.

l  Clock: Clock is anotherimportant component of CPU, which measuresand allocates a fixed time slot for processing each and every micro-operation (smallest functional operation). In simple terms, CPU is allocatedone or more clockcycles to complete a micro-operation. CPU executes the instructions in synchronization with the clock pulse.

Theclock speed of CPU is measured in terms of Mega Hertz (MHz)or Millions of Cycles persecond. The clock speed of CPU varies from one model to another in the range

4.77 MHz (in 8088 processor) to 266 MHz (in Pentium II).CPU speed is also specified in terms of Millions of Instructions Per Second (MIPS) or Million of Floating Point Operations Per Second (MFLOPS).

The relation betweenvarious hardware components of a computersystem is depictedin the figure 1.1:

Task  Compare and contrast Arithmetic Logic Unit (ALU) and Control Unit.

Input Devices

Input devices are used to input data, information and instructions into the RAM. These are “stand-alone” data entry stations.These units usuallyhave a small processorattached to a keyboard and a visual display unit. The processorchecks for the accuracy of data at the time of entry.

The common input devices are mentionedbelow.

Keyboard

The keyboardis one of the most common input devices of computers. The layout of the keyboard is like that of the traditional QWERTY typewriter. Most keyboards have three sectionsof keys: the standardtyping keys, cursor movement keys and the numeric keypad. To help users enter numbers quickly, keyboard provides a numeric keypad that functions much like a 10-key calculator. To select the numeric keypad’s operation, we need to use the Num Lock key. Most PCs come with a standard keyboard, which is flat in appearance. Keyboard’s keys match with that of a typewriter. The keyboard also includes specialpurpose function keys,arrow and cursor control keys. The layout of a simple keyboard can be seen in the Figure 1.2.