After completing this unit, you will be able to:
·         Understand the parts of a computer system.
·         Understand the various Types of Computer Hardware.
·         Understand the units of measure for Computer Memory and Storage.
·         Understand Input and Output Devices.
·         Understand Storage Devices.
·         Understand the different Computer software available.
1.1   Introduction
1.2   Essential Elements of a Computer
1.3   Types of Hardware
1.4   Types of Software
1.5   Types of Computers
1.6   History of Computers
1.7   Summary
1.8   Self-Assessment Questions
These days, it has become almost mandatory to have a general understanding of computers, its capabilities as well as its limitations. You need to know how to work with a computer by using pre-written instructions and commands that cause the machine to produce the results you desire. You may be surprised to know that much of your future work activity can be anticipated now, and that your career choice may make little difference in the accuracy of the forecast. In the 1950s, people considered computers to be large and costly. They thought that these machines would have little impact on their lives. In the 1960s, their thinking started changing. In the 1970s, organizations replaced their old and bulky computers with new versatile ones as they started realizing the benefits that could be accrued from them. By the mid-1980s, personal computers had flooded all types of organizations. Today, hospitals, supermarkets, provision stores, banks, business organizations, offices, factories, schools and numerous other institutions use computers for improving their productivity as well as for exercising better control on men, machinery and finances. Almost each and every section of society today is becoming more and more dependent on computers and information technology.
A computer is an electronic device used to process data. A computer can convert data into information that is useful to people. A computer is a programmable machine that manipulates raw, facts according to a set of instructions that are fed into it. A computer is a machine and all the other equipment associated with it constitute its hardware components.
The term computer is a general term that refers to an electronic data processing machine used by several persons to produce desired results as and when required. A Personal Computer (PC) refers to an electronic data processing machine meant for individual use. The instructions that direct the PC as to what it should do is called software. A set of instructions that perform a particular task is called the program, or software program. The instructions in the program direct the computer to perform input operations, process the data and output the results. The two basic types of computers are the analog and the digital computer. When talking about computers, we mostly refer to the digital type of electronic machines.
There are two basic kinds of computers: analog and digital.
Analog computers are analog devices. They have continuous states rather than discrete numbered states. An analog computer can represent fractional irrational values exactly, with no rounding-off.  Analog computers are usually used to process analog data and needs high processing capacity and a focused setup for it.
Digital computers are programmable machines that use discrete states. A binary digital computer uses two discrete states, such as positive/negative, high/.low or on/off, used to represent the binary digits zero and one. Nowadays, most of the computers are of a digital type as it is more flexible and can be easily adapted in our routine work.
Computers display the following characteristics depending on their type and use:
1.       The ability to perform calculations at a fast speed and to store that information for future retrieval or use.
2.       The ability to take in information and to store that information for future retrieval or use.
3.       The ability to take in and store a small variety of instructions for computers to obey.
4.       The ability to use simple logical rules to make decisions for their own internal control or for the control of some external activity.
5.       The ability to communicate with other computer systems.
6.       It has high diligence power.
7.       It is known for accurate result. (Note: The accuracy of the the results is based on the accuracy of the input)
8.       Computers are programmable to perform certain task, due to this feature they are more popular and are implemented in almost all of the area where data processing is required.
Part of Computer System
1.       Hardware
2.       Software
3.       Data
4.       Users
1.       Hardware
A computer’s hardware consists of electronic devices; the parts you can see and touch. The term “device” refers to any piece of hardware used by the computer, such as a keyboard, monitor, modem, mouse, etc.
2.       Software
Software, also called as programs, consists of Software, also called as programs, consists of organized sets of instructions for controlling computer operations. Some programs exist for the computer’s use, to help it manage its own tasks and devices.
Other programs exist for the user, and enable the computer to perform tasks for you, such as creating documents, deleting documents, etc.
3.       Data
Data consists of raw facts and figures which the computer can manipulate and process into information that is useful to people. Computerized data is digital, meaning that it has been reduced to digits or numbers. The computer stores and reads all data as numbers. Although computers use data in digital form, they convert data into forms that people can understand, such as text, numerals, sounds and images.
4.       User
People are the computer's operators or users.
Some types of computers can operate without much intervention from people; however personal computers are designed specifically for users.
Computer's hardware devices are categorized as follows:
1.       Processor (CPU)
2.       Memory
3.       Input and Output (I/O) Devices
4.       Storage Devices
1.       Processor ( central Processing Unit)
The processor is the part of the computer that actually does the computations. The procedure that transforms raw data into useful information is called processing. This function is divided between the computer’s processor and memory. The processor which is called the central processing unit (CPU) is also called as the brain of the computer. CPU controls each and every action of every component connected to it to make up the computer as a whole. It manages all devices and performs the actual processing of data. The CPU consists of one or more chips attached to the computer’s main circuit board (the motherboard). Some computers have more than one processor. This is called multi-processing.
The major kinds of digital processors are CISC, RISC, DSP and Hybrid.
CISC stands for Complex Instruction Set Computer. Mainframe computers and minicomputers are CISC processors, with manufacturers competing to offer the most useful instruction sets. Many of the first two generations of microprocessors were also CISC.
RISC stands for Reduced Instruction Set Computer. RISC came about as a result of academic research that showed that a small well-designed instruction set running compiled programs at high speed could perform more computing work than a CISC running the same programs (although very expensive).
DSP stands for Digital Signal Processing. DSP is used primarily in dedicated devices such as modems, digital cameras, graphics cards and other specialty devices.
Hybrid processors combine elements of two or three of the major classes of processors.
2.        Memory
Memory also consists of chips attached to the motherboard. The memory holds data and program instructions as the CPU works with them. This memory is called Random Access Memory (RAM).
The CPU can find any piece of data in the RAM as and when it needs it for processing. RAM is volatile, meaning it holds data only when the power is on; as soon as the power is off, the data which it holds is also erased automatically.
RAM, Random Access Memory, is a kind of internal memory available, which the CPU can access at any time whenever required. RAM is called “random access” because the processor or computer can access any location in the memory whenever required. RAM has been made from reed relays, transistors, integrated circuits, magnetic core or anything that can hold and store binary values (one/zero, plus/minus, open/close, positive/negative, high/low, etc.). Most modem RAM is made from integrated circuits.
RAM is available as Static RAM and Dynamic RAM. Static RAM is called static because it will continue to hold and store information even when the power is cut off or removed. Magnetic core and reed relays are examples of static memory. Dynamic RAM is called dynamic because it loses all data when the power is removed. Transistors and integrated circuits are examples of dynamic memory. It is possible to have battery backup for devices that are normally dynamic so as to turn them into static memory.
ROM is Read Only Memory (it is also random access, but only for reading). ROM is typically used to store things that will never change for the life of the computer, such as low level portions of an operating system. Some processors (or variations within processor families) might have RAM and/or ROM built into the same chip as the processor (normally used for processors used in standalone devices, such as arcade video games, ATMs, microwave ovens, car ignition systems, etc.). EPROM is Erasable Programmable Read Only Memory, a special kind of ROM that can be erased and reprogrammed with specialized equipment (but not by the processor it is connected to). EPROMs allow makers of industrial devices (and other similar equipment) to have the benefits of ROM, yet also allow for updating or upgrading the software without having to buy new ROM and throw out the old (the EPROMs are collected, erased and rewritten centrally, and then placed back into the machines).
Measuring Memory:
The smallest usable unit of measure for memory is the byte which is the amount of memory required to hold one character, like the letter of the alphabet A or the numeral 2.
Table 1.1
Approximate Value (bytes)Actual Value (bytes)Unit
1,0001,024Kilobyte (KB)
1,000,0001,048,576Megabyte (MB)
1,000,000,0001,073,741,824Gigabyte (GB)
1,000,000,000,0001,099,511,627,776Terabyte (TB)
3.        Input and Output Devices
Input devices are devices that bring information into a computer. Input devices accept data and instructions from the user or from another computer system. The keyboard and mouse are examples of input devices. Pure input devices include such devices as punched card readers, paper tape readers, keyboards, mouse, drawing tablets, touch pads, trackballs and game controllers. Input devices act as a feeding unit to the CPU for processing.
Output devices are devices that bring information out of a computer. Output devices return processed data back to the user or to another computer system. The printer and monitor are examples of output devices. Pure output devices include such devices as card punches, paper tape punches, LED displays (for light emitting diodes), monitors, printers and pen plotters. The output unit is responsible for displaying the required information in the desired format to the user.
Communication Devices
Communication devices (such as modems and network interface cards) perform both input and output functions allowing computers to share information. External modems are communication devices that computers utilize to connect to public networks like the Internet, A modem that sits inside the computer is called an internal modem, while modems that sit outside the computer are external modems. The type of modem you require depends on the type of Internet access service you desire. There are two general categories: Basic dial-up service and high-speed broadband service.
In order for a computer to be able to talk to other computers or to an Internet service provider, it needs what is called a Network Interface Card or NIC. This card, usually found inside the computer, is the gateway into which you plug an Ethernet cable. The Ethernet cable resembles a telephone wire, though slightly larger in diameter and its end is about twice the size of a standard RJ11 jack. An Ethernet cable is standard for connecting your computer to a high-speed Internet modem, or to a network within your home.
4.       Storage Device
Storage devices hold data not currently being used by the CPU. Data is commonly stored o a magnetic or optical disk. Each type uses a special medium for storing data on its surface. A disk drive is a device that reads data from and writes data onto a disk. Most new computer feature a floppy disk drive, a hard disk drive and an optical disk drive.
The most common optical storage devices are CD-ROM and DVD-ROM drives.
Software is a set of electronic instructions that tells the computer how to do certain tasks. A set of instructions is often called a program.
When a computer is using a particular program, it is said to be running or executing the program.
The two most common types of programs are system software and application software.
1.       System Software
System software exists primarily for the computer itself, to help the computer perform specific functions. One major type of system software is the operating system (OS). All computers require an operating system.
The OS tells the computer how to interact with the user and its own devices. Common operating systems include Windows, the Macintosh OS, OS/2, and UNIX. Basically one can conclude that system software is software which manages the memory, the processes and the files created by the user.
Operating System
An operating system is a complex series of programs, which controls the overall operations of a computer. It makes the power of the computer available to users. It allows users to communicate with a computer. It permits users to create files, use and control input/output devices and execute programs. MS-DOS is a single user operating system developed by Microsoft (a software company). MS-DOS stands for Microsoft Disk Operating System. It is widely used for personal computers PC, PC/XT and PC/AT. PC-DOS is the IBM version of this operating system. OS/2 is a multitasking operating system developed by Microsoft and IBM. It is used for personal computers PS/2 and PC/AT. UNIX is a multitasking and multi-user operating system developed by Bell Telephone Research Laboratory. It is used with mainframe, mini and powerful 32-bit personal computers. XENIX is a version of UNIX, developed by Microsoft. It is a widely used multi-user operating system. FINDER is an operating system for icon/mouse oriented personal computers such as Macintosh. RMX 86 is a multitasking operating system for real-time control in an industrial environment. In an industry, a number of tasks are performed on the basis of priority. The time-slice approach of UNIX is quite suitable for multi-user tasks but not suitable for priority oriented multitasking operations. RMX 86 has been developed by Intel for this type of environment. Windows 3.1 and Windows 95 Windows is a relatively recent operating system environment for PCs, developed by Microsoft Corporation. It provides Graphical User Interface (GUI). Earlier, graphical user interface was treated as a luxury and was not available to persons working in business environments with PCs. It was available to persons working on mini and large computers and desktop publishing systems. Today, almost all environments related to management, finance, sales, marketing, development and other general office functions need a rapid access to information. They also need powerful tools to manipulate, analyze, exchange and present information. Windows with its graphical user interface facility is capable of meeting these requirements.
2.       Application Software
Application software tells the computer how to accomplish tasks the user requires, such as creating a document or editing a graphic image.
Some important kinds of application software are:
a.       Word processing programs
b.      Spreadsheet software
c.       Database management
d.      Presentation programs
e.      Graphics programs
f.        Networking software
g.       Web design tools and browsers
h.      Internet applications
i.         Communications programs
j.        Utilities
k.       Entertainment and education
l.         Multimedia authoring
Computers can either be classified according to their size or their processing mode.
The different types of computers are as follows:
1.       Microcomputers
2.       Minicomputers
3.       Mainframe computers
4.       Supercomputers
1.       Microcomputers
A microcomputer is a low-cost, small, digital computer. It contains a microprocessor as its CPU, a memory unit, an input device and an output device. The word length of a microcomputer lies in the range 8-32 bits. Microcomputers have a wide range of applications. A few examples are: general purpose calculations, industrial control, instrumentation, home appliances, commercial equipment control, fuel injection control of a car, office automation, etc. PCs and PS/2 are microcomputers for general purpose computations. Users can work on PCs and PS/2 in high-level languages such as BASIC, FORTRAN, COBOL, PASCAL, etc. Popular application packages such as word processing, spreadsheet, database management, graphics, accounting packages, etc. also run on PCs and PS/2.
2.       Minicomputers
Minicomputers work faster and have more powerful CPUs than microcomputers. Their word length is 32 bits. Most minicomputers use Motorola 68030 or 68040 CPU. Some minicomputers are uni-processor systems whereas some are multiprocessor systems. The processing speed lies in the range 10-30 MIPS and Memory (RAM) capacity lies in the range 8-96 M bytes. In some systems it can be extended up to 128-256 M byte. The hard disk capacity lies in the range 380-3 Gigabytes (GB). A minicomputer can support up to 64 or even more terminals. Minicomputers are extensively used for payroll preparation, accounting and scientific computation. High-performance workstations with graphics input/output capability use minicomputers. Minicomputers are used for multi-user and interactive applications in colleges, universities, research organizations, government organizations and industries. They are also used for real-time (industrial) controls and engineering design work. Minicomputers support a greater variety of peripheral devices.
Examples of minicomputers are:
IBM AS/400/B60.
VAX 8842 (VAX stands for Virtual Address Extension and are manufactured by Digital Equipment Corporation).
WIPRO S-68030V and S-6833V built around 68030 CPU.
WIPRO LANDMARK 860 (a supermini) built around Intel i860 CPU (a 64-bit RISC processor).
HP 9000 series 800 (super mini) built around Hewlett Packard's VLSI RISC processor.
HCL magnum built around 68030 CPU, and 68040.CPU.
3.       Mainframe Computers
Mainframe computers are very powerful large general purpose computers. They are faster and more powerful than minicomputers. Their word length may be 48, 60 or 64 bits memory capacity, 64-256 M byte, hard disk capacity, I - 10 G byte or more, and processing speed, 30-100 MIPS. They are used where large amounts of data are to be processed or very complex calculations are to be made, and these tasks are beyond the computing capacity of minicomputers. They are used in research organizations, large industries, large business and government organizations; banks and airline reservations where a large database is required. Examples of mainframe computers are:
IBM 4300 series (small to medium size models)
IBM 308X series (large models)
IBM 3090 series
4.        Supercomputers
Supercomputers are much faster and more powerful than main-frame computers. Their processing speed lies in the range 400-10,000 MIPS, word length 64-96 bits, memory capacity 256M byte and more, hard disk capacity 1000M byte and more, and machine cycle time 4-6 nano second (ns). Supercomputers are specially designed to maximize the number of floating point instructions per second (FLOPS) which is usually more than 1 gigaflop per second. A supercomputer contains a number of CPUs which operate in parallel to make it faster. They are used for massive data processing and solving very sophisticated problems. They are used for weather forecasting, weapons research and development, rocketing, aerodynamics, seismology, atomic, nuclear and plasma physics.
Examples of supercomputers are:
CRAY 3, (developed by Control Data Corporation)
SX-2 (developed by Nippon Electric Corporation, Japan)
SX-3R (25.6 GIGAFLOPS, NEC make)
H ITAC S-300 (32 GIGAFLOPS, Hitachi make) HITAC S-300 is the latest and fastest supercomputer. The cycle time of a supercomputer may be as low as 4 ns. In a single machine cycle, two 64-bit data can be added. Supercomputers have a limited use and limited market because of their very high price. They are being used at some research centres and government agencies involving sophisticated scientific and engineering tasks.
The first computing machine, called the abacus, was invented around 5,000 years ago and surprisingly is still in use today. This device allows users to make computations using a system of sliding beads arranged on a rack. Let us now look at the interesting history of computers:
In the 1600s:
The next major advancement in computers came around the mid-1600s.Blaise Pascal, a tax officer working on taxes for the French Government, decided in 1642 to build an adding and subtracting machine to help him figure the taxes. The machine was called the ‘Pascaline’ and consisted of eight gears that worked to calculate numbers. The machine encountered many problems and was always breaking down.
In the 1800s:
The real beginning of computers as we know them today came about in the early 1800s, with a British Mathematics Professor named Charles Babbage. He worked on two machines: the Analytical Engine and the Difference Engine. These machines were amazingly similar to the computers we know today. The machines were meant to read a program from punched cards, figure out and store the answers to different problems, and then print the answers on paper. Due this remarkable work, Charles Babbage is known as the ‘Father of Computers’.
In the early 1900s:
The next huge step for computers came with the invention of a machine which was capable of counting and recording information faster. This machine was called the ‘Tabulating Machine’ that read and sorted data from punched cards. Thanks to this machine, instead of taking seven and a half years to count the census information, a government is likely to take only three years.

Table 1.2 Generations of Electronic Computers
GenerationFirst Generation –ISecond Generation IIThird Generation IIIFourth Generation IV
TechnologyVacuum TubesTransistorsIntegrated Circuits (multiple transistors)Microchips (million of transistors)
SizeFilled an entire BuildingFilled half a roomSmallerTiny-Palm Pilot is as powerful as the old building-sized computer
The First Generation Computers: 1946-1956
The first generation computers were huge, slow, expensive and often undependable. They were characterized by having vacuum tubes that were often very big and gave off much heat. The invention of the vacuum tube was an extremely important step in the advancement of computers. Vacuum tubes were very similar to light bulbs. Their purpose was to act like an amplifier and a switch, and could also stop and start the flow of electricity instantly.
In 1946, J. Presper Eckert, and John Mauchly built the ENIAC (Electronic Numerical Integrator and Computer). This was an electronic computer that used thousands of vacuum tubes, which took up a lot of space and gave off a great deal of heat. The ENIAC led to other vacuum tube type computers like the EDVAC (Electronic Discrete Variable Automatic Computer) and the UNIVACI (Universal Automatic Computer).
The Second Generation: 1957-1963
The second-generation computers used transistors instead of vacuum tubes. The transistor was much faster, reliable, smaller and cheaper to build than the previous vacuum tubes. Transistors were also found to conduct electricity faster and better than vacuum tubes. They were also much smaller and gave off virtually no heat as compared to the big vacuum tubes. Transistors were a tremendous breakthrough in the evolution of computers.
The Third Generation: 1964-1970
The integrated circuit, also called the semiconductor chip, is a single silicon chip packed with hundreds of transistors. The idea of placing such large number of transistors on a
single chip increased the power of a single computer and lowered its cost considerable. Ever since this invention, the number of transistors that can be placed on single chip further doubled every two years and the size and cost of computers have decreased even further.
The Fourth Generation: 1971-Today
The monolithic integrated circuit is an invention that put millions of transistors onto one integrated circuit chip (as opposed to just hundreds). By putting millions of transistors onto one single chip, more calculations and faster speeds could be reached by computers, However, what really triggered the tremendous growth of computers and its significant impact on our lives is the invention of the microprocessor (a single chip that could do all the processing of a full-scale computer).
A chip, the size of a pencil eraser that could do all the computing and logic work of a computer called the microprocessor was made to be used in calculators, not computers. It led to the invention of personal computers or microcomputers.
The Fifth Generation: The Future
The computers of the next generation will have millions upon millions of transistors on one chip and will perform over a billion calculations in a single second. The next generation of computers is also exploring artificial intelligence and is moving rapidly ahead. Obviously, there is much more to come in the future of computers and one can only guess what will come next. Let us wait and watch!
In this unit, you have studied about the basics of computers, the elements which include data, users, hardware and software. You should now be comfortable with the basic concepts and evolution of computers.
A computer is an electronic device capable of fast processing.
An analog computer can represent fractional or irrational values exactly, with no round-off required. Analog computers are usually used to process analog data and need high processing capacity and a focused setup for it.
A digital computer on the other hand is a programmable machine. A digital computer uses discrete states. A binary digital computer uses two discrete states, such as positive/negative, high/low, on/off, used to represent the binary digits zero and one.
Hardware is anything around the computer which is associated with the PC and can be touched and felt such as the keyboard and mouse.
Software is a logical entity which is usually a set of programs guiding the computer to perform certain tasks.
Data is a collection of facts, figures and symbols which is usually an input to the computer for processing information.
Users are usually the computer operators.