Class XI | CHAPTER 1

Computer Fundamentals

Introduction

Computers are seen everywhere around us, in all spheres of life. May it be the field of education and research, travel and tourism, weather forecasting, social networking, ecommerce or any other, computers have now become an indispensable part of our lives. The  manner,  in  which  computers  have  revolutionized  our  lives  because  of  their accuracy and speed of performing a job, is truly remarkable. Today no organization can function without a computer. In fact various organizations are trying to become paper free owing to benefits of computers. But the computers of today have evolved over the years from a simple calculating device to the portable high speed computers that we see today.

Evolution of Computers

The growth of computer industry started with the need for performing fast calculations. The  manual  method  of  computing  was  slow  and  prone  to  errors.  So  attempts  were made  to  develop  faster  calculating  devices.  The  journey  that  started  from  the  first calculating  device  i.e.  Abacus  has  led  us  today  to  extremely  high  speed  calculating devices.  Let  us  first  have  a  look  at  some  early  calculating  devices  and  then  we  will explore various generations of computer.

Abacus

Abacus was discovered by the Mesopotamia's in around 3000 BC. An abacus consisted of beads on movable rods divided into two parts. (Fig-1) Addition and multiplication of numbers  was  done  by  using  the  place  value  of  digits  of the  numbers  and  position  of beads in an abacus.

An Abacus

The Chinese further improved on the abacus so that calculations could be done more easily.  Even  today  abacus  is  considered  as  an  apt  tool  for  young  children  to  do calculations.  In an abacus, each row is thought of as a ten’s place. From right to left , row  no-1  represents  the  one’s  column  and  the  second  column  represents  ten’s  place. The third column represents the hundred’s place and so on. The starting position of the top beads (representing the value of five) is always towards the top wall of the abacus while the lower beads (representing the value of one) will always be pushed towards the lower wall as a starting position.

Napier’s Logs and Bones

The  idea  of  logarithm  was  developed  by  John  Napier  in  1617.  He  devised  a  set  of numbering  rods  known  as  Napier’s  Bones  through  which  both  multiplication  and division  could  be  performed.  These  were  numbered  rods  which  could  perform multiplication  of  any  number  by  a  number  in  the  range  of  2-9.  There  are  10  bones corresponding to the digits 0-9 and there is also a special eleventh bone that is used to represent  the  multiplier.  By  placing  bones  corresponding  to  the  multiplier  on  the  left side  and  the  bones  corresponding  to  the  digits  of  the  multiplicand  on  the  right  ,  the product of two numbers can be easily obtained.

Napier's Logs

Pascaline

Blaise  Pascal,  a  French  mathematician  invented  an  adding  machine  in  1642  that  was made  up  of  gears  and  was  used  for  adding  numbers  quickly.  This  machine  was  also called Pascaline and was capable of addition and subtraction along with carry-transfer capability. It worked on clock-work mechanism  principle.  It  consisted  of  various  numbered  toothed  wheels  having unique  position  values.  The  addition  and  subtraction  operations  was  performed  by controlled rotation of these wheels.

Pascaline

Leibnitz’s Calculator

In  1673  Gottfried  Leibnitz,  a  German  mathematician  extended  the  capabilities  of  the adding machine invented by Pascal to perform multiplication and division as well. The multiplication  was  done  through  repeated  addition  of  numbers  using  a  stepped cylinder each with nine teeth of varying lengths.

Leibnitz’s Calculator

Jacquard’s Loom

In order to make the cotton weaving process automatic, Joseph Jacquard devised punch cards  and  used  them  to  control  looms  in  1801.  The  entire  operation  was  under  a program’s control. Through this historic invention, the concept of storing and retrieving information started.

Difference engine and Analytical Engine

Charles  Babbage,  an  English  mathematician  developed  a  machine  called  Difference Engine  in  1822  which  could  calculate  various  mathematical  functions,  do  polynomial evaluation by finite difference and theoretically could also solve differential equations.

Thereafter in 1833, he designed the Analytical Engine which later on proved to be the basis  of  modern  computer.  This  machine  could  perform  all  the  four  arithmetic operations as well as comparison. It included the concept of central processor, memory storage  and  input-output  devices.  Even  the  stored  information  could  be  modified.

Owing back to the lack of technology of the time, the Analytical Engine was never built. Its design remained conceptual.

Both these great inventions earned him the title of ‘Father of Modern Computers’.

Difference Engine and Analytical engine

Mark 1

In 1944 Prof Howard Aiken in collaboration with IBM constructed an electromechanical computer named Mark 1 which could multiply two 10 digit numbers in 5 seconds. This machine  was  based  on  the  concept  of  Babbage’s  Analytical  engine  and  was  the  first operational  general  purpose  computer  which  could  execute  preprogrammed instructions automatically without any human intervention.

Mark 1

In 1945, Dr. John Von Neumann proposed the  concept of a stored program computer. As per this concept the program and data could be stored in the same memory unit. The basic architecture of the Von Neumann computer is shown in the figure below

Von Neumann Computer

According to Von Neumann architecture, the processor executes instructions stored in the  memory  of  the  computer.  Since  there  is  only  one  communication  channel,  the processor at a time can either fetch data or an instruction. That means at one point of time either the data or an instruction can be picked (fetched) from the storage unit for execution  by  the  processor.  Hence  execution  takes  place  in  sequential  manner.  This limitation of Von Neumann Computer is known as Von Neumann bottleneck. EDVAC (Electronic  Discrete  Variable  Automatic  Computer)  was  the  first  stored  program computer  developed  in  1952.  After  the  invention  of  first  electronic  computer  ENIAC (Electronic  Numerical  Integrator  and  Calculator)  in  1946,  the  computer  technology improved tremendously and at very fast pace.

Generation of Computers

Growth  in  the  computer  industry  is  determined  by  the  development  in  technology. Each  phase/generation  of  computer  development  is  characterized  by  one  or  more hardware/software  developments  that  distinctly  improved  the  performance  of  the computers of that generation. Based on various stages of development, computers can be divided into different generations.

The First Generation (1942-1955)

The  first  generation  computers  used  the  concept  of  ‘stored  program’  and  were characterized  by  vacuum  tubes.  A  vacuum  tube  is  a  delicate  glass  device  that  can control and amplify electronic signals. The first generation computers were made using thousands of vacuum tubes and were the fastest calculating devices of their time. These computers were very large in size, consumed lot of electricity and generated lot of heat. UNIVAC  1  was  the  first  electronic  computer  of  this  generation  and  was  used  for business applications.

Salient features of First generation computers:

 Used vacuum tubes to control and amplify electronic signals

 Huge computers that occupied lot of space

 High electricity consumption and high heat generation

 Were unreliable since they were prone to frequent hardware failures

 Commercial production was difficult

 They were very costly and required constant maintenance

 Continuous air conditioning was required

 Programming was done in machine language although assembly language also

started at the end of this generation Example : ENIAC , EDVAC , UNIVAC 1

Note: ENIAC weighed about 27 tons, was of the size 8 feet * 100 feet * 3 feet and

consumed around 150 watts of power.

The Second Generation (1955–1964)

The second generation computers were characterized by transistors. A transistor is a

solid state semiconductor device that revolutionized the electronic industry. Transistors

were smaller, highly reliable, consumed less electricity and generated less heat. Also

magnetic core memories were developed during this generation. These are tiny ferrite

rings that can be magnetized in either clockwise or anticlockwise direction so as to

represent binary 1 or binary 0. Magnetic cores were used as primary memories. Later

magnetic disks also came into existence and were used as secondary storage devices.

All these new developments – transistors, magnetic core memory and magnetic disk

storage devices made the computers more powerful and reliable. This further led to the

existence of operating systems. Programming languages like FORTRAN, COBOL, Algol

etc. also developed. Commercial applications of the computer increased and now the

computers were used in business and industries for applications like payroll, employee

management, inventory control etc. IBM 1401 and IBM 1620 were popular computers of

this generation.

Salient Features of Second generation computers:

 Use transistor based technology

 Were smaller and less expensive as compared to first generation

 Consumed less electricity and emitted less heat

 Magnetic core memories and magnetic disks were used as primary and

secondary storage respectively

 First operating system developed

 Programming in assembly language and in the later part high level languages

were used

 Wider commercial use but commercial production was still difficult

 They also required constant air-conditioning.

Examples: IBM 1401, IBM 1620, UNIVAC 1108

The Third Generation (1964-1975)

In 1964, the Integrated Circuits or ICs or chips revolutionized the electronic industry

and started the third generation of computers. An IC is a small silicon chip or wafer

made up of extremely purified silicon crystals. It has numerous transistors, capacitors,

resistors and other elements of an electronic circuit. A small scale integration (SSI) chip

used to have about 10 transistors on a single chip and a medium scale integration (MSI)

chip had about 100 transistors per chip. The size of memories also increased. Various

mainframe computers and minicomputers were developed during this generation. Even

operating systems with multitasking and multiprogramming features (you will learn

about these terms in the next chapter) were developed. Since ICs made the computers

highly reliable, relatively inexpensive and faster, computers these days were found in

areas of education, small businesses and offices along with industrial and business

applications. IBM 360 was a very popular third generation computer.

Salient Features of Third Generation computers:

 Used integrated circuits

 Computers were smaller , faster and more reliable

 Low power consumption and less emission of heat as compared to previous

generations

Examples: IBM 360 series, Honeywell 6000 series

The Fourth Generation (1975 onwards)

In this generation Large Scale Integration (LSI) and Very Large scale integration (VLSI)

technology was used by which up to 300,000 transistors were used on a single chip.

Thus integration of complete CPU on a single chip was achieved in 1971 and was

named microprocessor which marked the fourth generation of computers. The

computers based on microprocessor technology had faster accessing and processing

speeds. In addition to this the increased memory capacity further made the computers

more powerful and also more efficient operating systems were developed for these

computers. New concepts of microprogramming, application software, databases,

virtual memory etc were developed and used.

The computers that we use today belong to this generation. These portable computers

can be carried from one place to another owing to their compact size. They are much

more accurate. Even memory sizes have become phenomenal. Commercial production

of these computers is easier and they are the least expensive, compared to the earlier

generation computers.

Also computer networks starting coming up during this generation. It is today one of

the most popular means to interact and communicate with people.

Salient features of Fourth generation Computers

 ICs with LSI and VLSI technology

 Microprocessors developed

 Portable computers developed

 Networking and data communication became popular

1 1

 Different types of secondary memory with high storage capacity and fast access

developed

 Very reliable ,powerful and small in size

 Negligible power consumption and heat generation

 Very less production cost

Fifth Generation Computers

Fifth Generation computers are still under development. This generation is based on the

concept of artificial intelligence. In simple terms the computers of this generation are

supposed to behave like humans. The principles of parallel processing (many

processors are grouped together) and superconductivity are being used to develop

devices that respond to human languages and will have the ability to apply previously

gained knowledge to execute a task. They will let them make decisions of their own to

execute a task. Some applications like voice recognition, visual recognition are a step in

this very direction.

Salient features of fifth generation computers:

 Parallel Processing

 Superconductivity

 Artificial Intelligence

Computer - Data and Information

We all know what a computer is? It is an electronic device that processes the input

according to the set of instructions provided to it and gives the desired output at a very

fast rate. Computers are very versatile as they do lot of different tasks such as storing

data, weather forecasting, booking airline, railway or movie tickets and even playing

games.

Data: It is the term used for raw facts and figures. For example, 134, + 9, ‘Raju’, ‘C’ are

data. Definition of information should start from next line as given in the word file. In

composed file it is starting from the same line immediately after the definition of data.

Information: Data represented in useful and meaningful form is information. In simple

words we can say that data is the raw material that is processed to give meaningful,

ordered or structured information. For example Raju is 9 years old. This is information

about Raju and conveys some meaning. This conversion of data to information is called

data processing.

Functional Components of a Computer

The computer is the combination of hardware and software. Hardware are the physical

components of a computer like motherboard, memory devices, monitor, keyboard etc.

while software is the set of programs or instructions. Both hardware and software

together make the computer system function. Let us first have a look at the functional

components of a computer.

Every task given to a computer follows an Input- Process- Output Cycle (IPO cycle). It

needs certain input, processes that input and produces the desired output. The input

unit takes the input, the central processing unit does the processing of data and the

output unit produces the output. The memory unit holds the data and instructions

during the processing.

Fig below shows the basic structure of the computer.

Functional Components of a computer

Input Unit

The input unit consists of input devices that are attached to the computer. These devices

take input and convert it into binary language that the computer understands. Some of

the common input devices are keyboard, mouse, joystick, scanner etc.

Central Processing Unit (CPU)

Once the information is entered into the computer by the input device, the processor

processes it. The CPU is called the brain of the computer because it is the control centre

of the computer. As the CPU is located on a small chip, it is also called the

microprocessor. It first fetches instructions from memory and then interprets them so as

to know what is to be done. If required, data is fetched from memory or input device.

Thereafter CPU executes or performs the required computation and then either stores

the output or displays on the output device. The CPU has three main components

which are responsible for different functions – Arithmetic Logic Unit (ALU) , Control

Unit (CU) and Memory registers.

Arithmetic and Logic Unit (ALU)

The ALU, as its name suggests performs mathematical calculations and takes logical

decisions. Arithmetic calculations include addition, subtraction, multiplication and

division. Logical decisions involve comparison of two data items to see which one is

larger or smaller or equal.

Control Unit

The Control unit coordinates and controls the data flow in and out of CPU and also

controls all the operations of ALU, memory registers and also input/output units. It is

also responsible for carrying out all the instructions stored in the program. It decodes

the fetched instruction, interprets (understands) it and sends control signals to

input/output devices until the required operation is done properly by ALU and

memory.

Memory Registers

A register is a temporary unit of memory in the CPU. These receive data/information

and then this data/information is held in them as per the requirement. Registers can be

of different sizes(16 bit , 32 bit , 64 bit and so on) and each register inside the CPU has a

specific function like storing data, storing an instruction, storing address of a location in

memory etc. The user registers can be used by an assembly language programmer for

storing operands, intermediate results etc. Accumulator (ACC) is the main register in

the ALU and contains one of the operands of an operation to be performed in the ALU.

Memory

Memory attached to the CPU is used for storage of data and instructions and is called

internal memory. During processing, it is the internal memory that holds the data. The

internal memory is divided into many storage locations, each of which can store data or

instructions. Each memory location is of the same size and has an address. With the

help of the address, the computer can find any data easily without having to search the

entire memory. The internal memory is also called the Primary memory or Main

memory. When the task is performed, the CU makes the space available for storing data

and instructions, thereafter the memory is cleared and the memory space is then

available for the next task. The time of access of data is independent of its location in

memory, therefore this memory is also called Random Access memory (RAM). Primary

memory is volatile in nature. That means when the power is switched off, the data

stored in this memory is permanently erased. That is why secondary memory is needed

to store data and information permanently for later use. Some of the examples of

secondary storage devices are hard disk, compact disks, pen drives etc.

Output Unit

The output unit consists of output devices that are attached with the computer. It

converts the binary data coming from CPU to human understandable from. The

common output devices are monitor, printer, plotter etc.

Interconnection between Functional Components

The interconnection between the functional components of a computer can be done in

many ways. In microcomputers we generally see a Common Bus Architecture as shown

in the figure below. As we have seen before that a computer consists of input unit that

takes input, a CPU that processes the input and an output unit that produces output.

All these devices communicate with each other through a common bus. A bus is a

transmission path (set of conducting wires) over which data or information in the form

of electric signals, is passed from one component to another in a computer. The bus can

be of three types – Address bus, Data bus and Control Bus.

Common Bus Architecture

The address bus carries the address location of the data or instruction. The data bus

carries data from one component to another and the control bus carries the control

signals. As shown in the figure above, the system bus is the common communication

path that carries signals to/from CPU, main memory and input/output devices. The

input/output devices communicate with the system bus through the controller circuit.

This controller circuit helps to manage various input/output devices attached to the

computer.

Concept of Booting

When the computer is switched on, a copy of boot program is brought from ROM into

the main memory. This process is called booting. The CPU first runs a jump instruction

that transfers to BIOS (Basic Input output System) and it starts executing. The BIOS

conducts a series of self diagnostic tests called POST (Power On Self Test). These tests

include memory tests, configuring and starting video circuitry, configuring the system’s

hardware and checking other devices that help to function the computer properly.

Thereafter the BIOS locates a bootable drive to load the boot sector. The execution is

then transferred to the Boot Strap Loader program on the boot sector which loads and

executes the operating system. If the boot sector is on the hard drive then it will have a

Master Boot record (MBR) which checks the partition table for active partition. If found,

the MBR loads that partition’s boot sector and executes it.

Booting Process is of two types – Warm and Cold

Cold Booting: When the system starts from initial state i.e. it is switched on, we call it

cold booting or Hard Booting. When the user presses the Power button, the instructions

are read from the ROM to initiate the booting process.

Warm Booting: When the system restarts or when Reset button is pressed, we call it

Warm Booting or Soft Booting. The system does not start from initial state and so all

diagnostic tests need not be carried out in this case. There are chances of data loss and

system damage as the data might not have been stored properly.

Classification of Computers

The computers can be classified based on the technology being used as: Digital, Analog

and Hybrid

Digital Computers

These computers are capable of processing information in discrete form. In digital

technology data which can be in the form of letters, symbols or numbers is represented

in binary form i.e. 0s and 1s. Binary digits are easily expressed in a digital computer by

the presence (1) or absence (0) of current or voltage. It computes by counting and

adding operations. The digital computers are used in industrial, business and scientific

applications. They are quite suitable for large volume data processing.

Analog Computers

An analog computer works on continuously changeable aspects of physical

phenomenon such as fluid pressure, mechanical motion and electrical quantities. These

computers measure changes in continuous physical quantities say current and voltage.

These computers are used to process data generated by ongoing physical processes. A

thermometer is an example of an analog computer since it measures the change in

mercury level continuously. Although the accuracy of an analog computer is less as

compared to digital computers, yet it is used to process data generated by changing

physical quantities especially when the response to change is fast. Most present day

analog computers are well suited to simulating systems. A simulator helps to conduct

experiments repeatedly in real time environment. Some of the common examples are

simulations in aircrafts, nuclear power plants, hydraulic and electronic networks.

Hybrid Computers

These use both analog and digital technology. It has the speed of analog computer and

the accuracy of a digital computer. It may accept digital or analog signals but an

extensive conversion of data from digital to analog and analog to digital has to be done.

Generally the analog components provide efficient processing of differential equations

while the digital part deals with logical operations of the system. Hence benefits of both

analog and digital computing are readily available. Hybrid Computers are used as a

cost effective means for complex simulations.

Classification of Digital Computers

The digital computers are classified according to their computing capabilities. The

various types of digital computers are discussed below:

Micro Computers

These are also known as Personal Computers. These type of digital computer uses a

microprocessor (a CPU on a single chip) and include both desktops and laptops. These

computers can work on small volume of data, are very versatile and can handle variety

of applications. These computers are being used as work stations, CAD, multimedia

and advertising applications. Small portable computers such as PDAs (Personal Digital

Assistants) and tablets with wireless computing technology are increasingly becoming

popular.

Mini Computers

These computers can support multiple users working simultaneously on the same

machine. These are mainly used in an organization where computers installed in

various departments are interconnected. These computers are useful for small business

organizations.

Main Frames

These computers are large and very powerful computers with very high memory

capacity. These can process huge databases such as census at extremely fast rate. They

are suitable for big organizations, banks, industries etc. and can support hundreds of

users simultaneously on the network.

Super Computers

These are fastest and very expensive computers. They can execute billions of

instructions per second. These are multiprocessor, parallel systems suitable for

specialized complex scientific applications involving huge amounts of mathematical

applications such as weather forecasting. The main difference between a supercomputer

and a mainframe is that a supercomputer executes fewer programs as fast as possible

whereas a mainframe executes many programs concurrently.