Computer Science

Key Unit Competency

By the end of the unit, you should be able to explain characteristics and evolution of
computers and appreciate impact of computers in the society.
Unit Outline
• Definition of computer science.
• Characteristics of computer.
• Classification of computer.
• Role of computers in society.
• History of computers.

Introduction
In the current generation, use of computers has become a common practice in classrooms, business, offices, entertainment, health, broadcasting, and many
other areas. In this section, we discuss fundamental concepts, and characteristics,
applications and evolution of computers.

1.1 Definition of a computer and computer science

To adapt to the ever changing technologies, there is need to understand fundamental
concepts, and characteristics of computers.

Activity 1.1: Definition and parts of a computer
1. In groups of three, use search engines such as Google, or Bing to search for
standard definitions of the following terms:
• Computer
• Computer Science
2. Fig. 1.1 below shows a typical type of a computer. Define and name the parts
labelled (a) to (d).

1.1.1 Definitions

Computer: A computer is an electronic device capable of receiving raw facts (data) and performing a sequence of operations on the data based on special computer instructions (processing) to produce desired output (information). Fig. 1.2 below illustrates this process.

Computer Science: Computer science is a branch of science that deals with theory of computation, or design and operation of computer hardware and software, and of the application of computers in all sectors.

Activity 1.2: Computer science
1. Do some research on the internet and write an essay on areas of study within Computer Science. These may include artificial intelligence, information systems, networks, security, database systems, human computer interaction, vision and graphics, numerical analysis, programming, software engineering, health informatics, bioinformatics and computational theories.
2. Identify other fields of study that are related to Computers Science offered in most colleges and universities in Rwanda.

1.2 Characteristics of computers
Though humans are more intelligent than computers, much of the activities from business to space exploration are now carried out with the support of computers. Does this imply computers are better than human beings?

Activity 1.3: Characteristics of a computer
Individually, do some research and write an essay describing why computers though not as intelligent as human beings, have characteristics that have made them preferred tools in the workplace. Some of the characteristics that should appear in the essay include: reliability, speed, accuracy, diligence, versatility, memory, feelings, intellectual ability. Upon completion of the essay, you should be able to appreciate that although
computers do not have feelings and intelligence like human beings, they are:

1. Fast: A computer can perform in a few seconds the amount of work a human being can do in days, months or years.
2. Accurate: A computer is far much more accurate than human beings during data processing. The accuracy of the output obtained from a computer mainly depends on input provided. If the input is wrong, the computer processes wrong

output hence the term Garbage In Garbage Out (GIGO). GIGO is a phrase used in computer science that implies that if invalid or erroneous data is entered into a computer (garbage in), the computer will process and output invalid or erroneous results (garbage out).

3. Versatile: Computers are versatile i.e. flexible in that they can be used to carry out different types of activities. For example, at one point using a word processor a computer can be programmed to process words like a typewriter and while using a spreadsheet to perform calculations like a calculator.
4. Reliable: Computers are more reliable because they do not get tired or bored in processing repeated work.
5. Power of remembering: Computers can store and recall high amount of information depending with the size of secondary storage media.
6. Diligent: Computers do not suffer from human related traits such as tiredness, and loss of concentration after working for long hours.

1.3 Classification of computers
Activity 1.4: Classification of computer
1. In groups of three, use internet, magazines or other reference books to classify computers according to:
• Physical size and processing power.
• Functions they perform.
• Type of data they process.
2. Other than the above types of classifications, brainstorm on other factors that can be used to classify computers. Generally, computers can be classified using different criteria but the most common classifications are based on size, processing power, function, and type data processing.

1.3.1 Types of computers according to size and power
When classified by physical size and processing power, computers can either be supercomputers, mainframe computers, minicomputers or microcomputers.

1.3.1.1 Supercomputers
Supercomputers are the fastest, largest, most expensive and powerful computers available. They are able to perform many complex operations in a fraction of a second. Supercomputers are mainly used for scientific research, which requires enormous calculations. Some of the applications that justify use of supercomputers include aerodynamic design and simulation, petroleum research, defence and weapon analysis and telecommunications. Because of its weight, a supercomputer is kept in a special room as shown in Fig. 1.3.

                      Activity 1.5: Uses of supercomputers

By doing research, explain how supercomputers are used by National Aeronautics and Space Administration (NASA) for aeronautics and aerospace exploration.

                                        1.3.1.2 Mainframe computers
Mainframe computers such as shown in Fig 1.4 are less powerful and cheaper than supercomputers. While supercomputers may be described as giant computers, mainframes are said to be big in size. They are used for processing data and performing
complex mathematical calculations. They have a large storage capacity and can support a variety of peripherals. Mainframe computers are used as powerful data processors in large research institutions and organisations such as banks, hospitals
and airports, which have large information processing needs.

                                                 Activity 1.6: Mainframe computers

In groups, discuss and write a brief report on how mainframe computers are used in large organizations such as banks, hospitals, and airlines.

                                                             1.3.1.3 Minicomputers
Minicomputers shown in Fig. 1.5 are also known as small-scale mainframes because they were cheaper alternative to mainframes computers. Like mainframes, minicomputers are used in business organisations, laboratories, research institutions,
engineering firms and banks.

                                            Activity 1.7: Distinction between mainframe and minicomputers

In groups, use reliable sources on the internet draw clear distinctions between mainframe and minicomputers.

1.3.1.4 Microcomputers
A microcomputer is the smallest, cheapest and relatively least powerful type of computer. It is called a microcomputer because its CPU is called a microprocessor, which is very small compared to that of minicomputers, mainframes and supercomputers. Microcomputers are commonly used in schools, business enterprises, cybercafé, homes and many other places. Today, the processing power of microcomputers has increased tremendously close that of minicomputers and mainframes.
              

                                                           Types of Microcomputers
Microcomputers may be classified into desktop and portable computers. A desktop such as shown in Fig. 1.6 are common types of microcomputer designed to fit conveniently on top of a typical office desk, hence the term desktop.

Portable computers are microcomputers small enough to be held by hand (handheld) or placed on the laps while working (laptop). Examples of Portable computers include laptops (notebook), tablets, and smartphones. Fig. 1.7 shows illustrations of notebook PC and a tablet.

                                                             Activity 1.8: Types and uses of microcomputers
1. In the school environment, at home or in business organization, identify the following types of microcomputers:
• Desktop computers                               • Notebooks/Laptop
• Tablets                                                   • Palmtops
2. In discussion groups, research from reliable internet sites how the term microcomputer came into being.
3. Using the illustrations given below, identify each type of microcomputer.

                                            1.3.2 Types of computers according to functions

Regardless of the size and processing power, a computer can be classified according to functions they perform. In this case, we have servers, workstations and embedded computers. Servers and workstations are general purpose computers used to provide access to resources on a network while special purpose computers are dedicated to a single task.

                                    1.3.2.1 Servers
A server is a dedicated computer that provides hardware or software resources to other computers on a local area network (LAN) or a over the Internet. Unlike desktop computers that have standard input and output devices attached, most servers such as shown in Fig. 1.9 do not require such peripheral devices because they are accessed remotely using remote access software. Because servers are expensive, a powerful desktop computer may be converted into a server by adding the appropriate hardware and software resources.

Generally, servers may be classified according to the task they perform. For example, a file server provides massive storage devices dedicated to storing files while a print server is used to access to more printers, and a network server is a computer that manages network traffic.

                                                                1.3.2.2 Workstation

A workstation is a name given to a computer connected to a server or network intended to be used by one person at a time, they are commonly connected to a server.
This means that all users who utilize a computer at their job or school are using a workstation. Commercially, workstations are used for business or professional use such as graphics design, desktop publishing and software development.
                                        

                                       1.3.2.3 Embedded computers
Embedded computers are computing devices designed for a specific purpose. Generally, an embedded computer has an operating system that only runs a single application. Examples of embedded computing devices include dishwashers, ATM machines, MP3 players, routers, and point of sale POS terminals.

                                     Activity 1.9: Classification of computers
1. In the school environment, classify the following computers into servers, workstations, or embedded computers:
• Computer used to control access to hardware and software resources in a networked environment.
• Computer used to access hardware and software resources in a networked environment.
• Computer used in smart cards such as those used on ATMs and automated parking.
2. In your groups, discuss advantages and disadvantages of supercomputers over microcomputers.

                                1.3.3 Types of computers according to data type
Computers can be classified into digital computers, analog computers or hybrid computers depending on the type of data they process.

                                    1.3.3.1 Digital computers
Digital computers perform calculations and logical comparisons by representing data and instructions as binary digits. This means that digital computers must convert data such as text, numbers, images, video and sound into a series of zeros and ones as represented by the signal waveform in Fig. 1.10. The data signal is either at 0V or 5V. In this case +5 or -5V represent a 1. Most of the computers used today such as desktop computers, laptops and tablets are digital computers.

                                                  1.3.3.2 Analog computer

These are computers that process data that is continuous (analog) in nature. An analog signal is one which has a value that varies smoothly from peak to minimum and vice versa.
For example, the sound waves that your mouth produces when you speak are analogue - the waves vary in a smooth way as shown in Fig 1.11. In the early days of computer evolution, most of the computers were analog in nature. Today analog
computers are specialized devices used in engineering and scientific applications unlike those used to measure speed, temperature and pressure data.

                                            Activity 1.10: Classification of computers

1. Research for details from the internet, magazines or other reference books and define the following types of computers:
• Analog computers
• Digital computers.
• Hybrid computers.
2. Discuss advantages and disadvantages of the three types of computers.

                                                Assessment Exercise 1.1

1. Explain some of the characteristics that make a computer suitable for processing repetitive tasks.
2. Differentiate between the following terms:
(a) Mainframe and minicomputers.
(b) Analog and digital data.
(c) Servers and workstations.
3. Draw a sketch of a desktop computer and label the main physical parts.

                                    1.4 Role of computers in society

Computers play very important roles in various socio-economic sectors such as economics, offices, financial institutions, industries, health, communication, security, education, entertainment and libraries. In this section, we discuss common application areas of computers in our society.

                                              1.4.1 Economics

Computers enables governments, businesses and individuals to plan, budget and tract their revenues and expenditures. Increased computing power means that it has become possible to perform economic analysis both at macro and micro-economic level.

                                              1.4.2 Retail stores

Most retail stores use computers to help in the management of daily activities like stock control. The stock control system keeps account of what is in stock, what is sold and what is out of stock. The management is automatically alerted whenever a particular item or items are running out of stock that need reordering.

                                                       1.4.3 Offices

Computers have increased efficiency in offices by reducing the time and effort needed to access and receive information. Most modern office functions have been automated for efficient service delivery.

                                                 1.4.4 Financial institutions

In the banking sector, computers and mobile devices such as cellphones can be used to withdraw or get any service from different branches. Special cash dispensing machines called automated teller machines (ATM’s) have enabled automation of cash deposits and withdrawal services. Efficiency has also been increased due to better record keeping and document processing brought about by use of computers.

                                                       1.4.5 Industries

Computers are being used to monitor and control industrial processes. The computer age has seen wide use of remote controlled devices called robots. A robot is a machine that works like a human being but performs tasks that are too unpleasant, dangerous, or complex and tedious to assign to human beings.

                                                            1.4.6 Health

Computers are used to keep patients’ records in order to provide easy access to a patient’s treatment and diagnosis history. Computerised medical devices are now being used to get a cross sectional view of the patient’s body that enables physicians to get proper diagnosis of the affected body parts with high levels of accuracy. Computers also control life support machines in Intensive Care Units (ICU).

                                                         1.4.7 Communication

Integration of computers and telecommunication facilities has made message transmission and reception to be very fast and efficient. Because of the speed with which information can be transmitted around the world using computers, the world is said to have become a global village.

                                                          1.4.8 Security

Information stored in computers such as fingerprints, images and other identification details help law enforcers carry out criminal investigations.

                                                            1.4.9 Education

Computers are used in teaching and learning in schools, colleges and universities. Learning and teaching using computers is referred to as Computer Aided Learning (CAL) and Computer Aided Instruction (CAI). For example, experiments in subjects like Chemistry or Physics may be demonstrated using a special computer program that can depict them on the screen through a process called simulation. To take care of learners with special needs, computers with software and assistive technologies
such as microphone, braile keyboards and text magnifiers have been developed.

                                                             1.4.10 Entertainment
Computers can be used at home for recreational activities such as watching movies, playing music and computer games. They can also be used in storing personal information, calculating, keeping home budgets and research.

                                                              1.4.11 Library management

In a modern library, computers enable library personnel to easily access and keep updated records of books and other library materials. Library users can also use computers to search for titles instead of using the manual card catalogue.

                                               Activity 1.11: Role of Computers in society
1. Match the following computer application areas numbered 1 - 8 with the role played in column numbered A - H.
1. Supermarket                                           A – Forensic investigations
2. Hospital                                                  B – Entertainment
3. Bank                                                      C – Stock control
4. Hotel                                                      D – Booking rooms
5. Home                                                     E – Analysing academic data
6. School                                                    F – Motor vehicle assembly
7. Industry                                                  G – Remote monitoring of patients
8. Police station                                         H – Processing cash transactions

2. Apart from using computers and other ICT devices such as mobile phones as productivity tools at home and workplace, they can be used to address various social, environental and cultural issues. Brainstorm on how computers can be used in Rwanda to promote:
• Peace and reconciliation.
• Ndi Umunyarwanda philosophy.
• Environmental management.
• Sexuality and moral values.

3. By visiting around and outside the school, discuss both positive and negative impact of computers in the following sectors:
• Education                                                      • Business
• Health                                                            • Entertainment
• Communication                                              • Security control
• Financial management                                   • Government

                                                      1.5 History of computers

The computer, as we know it today, had its beginning with a 19th century English mathematics professor name Charles Babbage. Babbage designed the Analytical Engine and that is considered as the basic architecture of modern electronic computers are based on. It is not until 1937 when John Atanasoff and Clifford Berry built the first electronic digital computer called Atanasoff-Berry Computer (ABC). Since then, there have been major computer evolutions classified into five generations.

                                            1.5.1 First generation (1940-1956): Vacuum tubes

The first generation computers used electronic components known as vacuum tubes or thermionic values (Fig. 1.12) for circuitry and magnetic drums for memory. These types of computers were enormous, expensive, consumed a lot of power, and emitted a lot of heat which was often the cause of malfunctions. Input was based on punched cards and paper tape, and output was displayed on printouts. The three popular examples of first generation computers are Electronic Numeric Integrator and Calculator (ENIAC), Electronic Discrete Variable Automatic Computer (EDVAC) and Universal Automatic Computer (UNIVAC).

                                                 Activity 1.12: First generation computers

In groups explain why first generation computers were large in size, emitted a lot of heat, and consumed a lot of power.

                                                  1.5.2 Second generation (1956-1964): Transistors

The invention of transistors shown in Fig. 1.13 ushered in the second generation of computers that were made up of transistors that are superior vacuum tubes. However, these computers but did not see widespread use in computers until the late 1950s.
Although transistors still generated a great deal of heat, they were faster and more reliable than those made of vacuum tubes. In terms of input, computers in second generation relied on punched cards while storage was on magnetic cores. Examples of second generation computers include IBM’s 1401 and 7070, UNIVAC 1107, ATLAS LEO Mark III and Honeywell H200.

                                                Activity 1.13: Second generation computers

Identify examples of second generation computers. By researching from Internet or other reliable reference, identify at least three examples of second generation computers.

                                                 1.5.3 Third generation (1964-1970): Integrated circuits

Development of electrical components known as integrated circuit (IC) was the hallmark of the third generation of computers. Fig. 1.14 shows illustration of ICs that are made up of transistors embedded on silicon chips called semiconductors. Most third generation computers allowed users to interact a computer through keyboards and monitors. For the first time, computers became accessible to a mass audience because they were smaller and cheaper than their predecessors. Examples of third generation computers include smaller and less expensive minicomputers such as IBM 360 and ICL 19000 series.

                                              Activity 1.14: Third generation computers

Through research identify at least three examples of third generation computers.

                                                  1.5.4 Fourth generation (1970-Present): Microprocessors

Further technological improvements on ICs saw very large intergrated (VLI) circuits which have thousands of integrated circuits built onto a silicon chip as microprocessor shown in Fig. 1.15. It is in the fourth generation computers that programs with graphical user interface (GUIs), mouse, and hand-held devices were introduced. Some the early examples of fourth generation computers include IBM 370 and 4300, Honeywell DPS-88 and Burroughs 7700.

                                1.5.5 Fifth generation (Present and beyond): Artificial intelligence

Tremendous improvement on hardware and software has given rise to what is loosely considered as the fifth generation computers that are based on artificial intelligence. The term artificial intelligence refers to capability of a computer to mimic human behaviour. The goal of fifth generation computing is to develop devices that are capable of learning, and respond to natural language input (voice recognition). In future, research outcomes in the fields of artificial intelligence and nanotechnology are expected to radically change the face of modern computers.

                                          Activity 1.15: Fifth generation computers

By researching from Internet or other reliable reference material, identify at least three examples of fifth generation computers
Table 1.1 gives a summary of some of the main technological specifications and uses of computers from the first to fifth generation.

1. Match the following generations of computers with the technology used to develop them.
1. First generation                                     A – Very large scale integrated circuit
2. Second generation                                B – Thermionic valves
3. Third generation                                    C – Transistors
4. Fourth generation                                  D – Integrated circuits
2. The age of modern electronic computers can be traced back to 1940s. In groups, discuss five generations that characterize modern electronic computers.

                                                            Unit Test 1

1. What were the characteristics of first generation computers?
2. Draw a block diagram showing the evolution of computers in their generations and characteristics per each.
3. Define the term artificial intelligence.
4. Explain how integrated circuits contributed to the development of microcomputers.
5. Highlight some of the achievements of the fifth generation computers.