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INTRODUCTION TO COMPUTERS.
Definition of a Computer:
A Computer is an electronic device that operates (works) under the control of programs stored in its own memory unit.
A computer is an electronic machine that processes raw data to give information as output.
An electronic device that accepts data as input, and transforms it under the influence of a set of special instructions called Programs , to produce the desired output (referred to as Information ).
A computer automatically accepts data & instructions as input from an Input device, stores them temporarily in its memory, then processes that data according to the instructions given, and finally transfers the processed data (Information) to an Output device.
Explanations;
A computer is described as an electronic device because; it is made up of electronic components and uses electric energy (such as electricity) to operate.
A computer has an internal memory, which stores data & instructions temporarily awaiting processing, and even holds the intermediate result (information) before it is communicated to the recipients through the Output devices.
It works on the data using the instructions issued, means that, the computer cannot do any useful job on its own. It can only work as per the set of instructions issued.
A computer will accept data in one form and produce it in another form. The data is normally held within the computer as it is being processed.
Program:
A computer Program is a set of related instructions written in the language of the computer & is used to make the computer perform a specific task (or, to direct the computer on what to do).
A set of related instructions which specify how the data is to be processed. A set of instructions used to guide a computer through a process.
Data:
Data is a collection of raw facts, figures or instructions that do not have much meaning to the user.
- Data may be in form of numbers, alphabets/letters or symbols, and can be processed to produce information.
TYPES OF DATA.
There are two types/forms of data:
a). Digital (discrete) data:
Digital data is discrete in nature. It must be represented in form of numbers, alphabets or symbols for it to be processed by a computer.
- Digital data is obtained by counting. E.g. 1, 2, 3 …
b). Analogue (continuous) data:
Analogue data is continuous in nature. It must be represented in physical nature in order to be processed by the computer.
- Analogue data is obtained by measurement. E.g. Pressure, Temperature, Humidity,
Lengths or currents, etc
- The output is in form of smooth graphs from which the data can be read.
Data Processing:
It is the process of collecting all items of data together & converting them into information.
Processing refers to the way the data is manipulated (or handled) to turn it into information.
The processing may involve calculation, comparison or any other logic to produce the required result. The processing of the data usually results in some meaningful information being produced.
Information:
Information is the data which has been refined, summarized & manipulated in the way you want it, or into a more meaningful form for decision-making.
- The information must be accurate, timely, complete and relevant.
Comparison between Data and Information.
Data Information
1. Unprocessed (raw) facts or figures.
2. Not arranged.
3. Does not have much meaning to the user.
4. Cannot be used for decision-making.
1. It is the end-product of data processing
(processed data)
2. Arranged into a meaningful format.
3. More meaningful to the user.
4. Can be used to make decisions.
Characteristics / Features of a Computer.
Before 20th^ century, most information was processed manually or by use of simple machines. Today, millions of people are using computers in offices and at home to produce and store all types of information
The following are some of the attributes that make computers widely accepted & used in the day- to-day activities in our society:
1. Speed.
Computers operate at very high speeds, and can perform very many functions within a very short time. They can perform a much complicated task much faster than a human being. The speed of a computer is measured in Fractions of seconds. Millisecond - a thousandth of a second (10-3) Microsecond - a millionth of a second (10-6) Nanosecond - a thousand millionth of a second (10-9) Picosecond - a million millionth of a second (10-12) The speed of a computer is usually linked to the technology used to build it. a). 1 st^ Generation computers (1940s & early 1950s). The computers were built using Vacuum tubes , and the speed was measured in Milliseconds. E.g., a computer could perform 5,000 additions & 300 multiplications per second. b). 2 nd^ Generation computers (1950s & early 1960s). Were built using Transistors. Their operation speeds increased & were measured in Microseconds. E.g., a computer could perform 1 million additions per second. c). Mid 1960s. Integrated Circuit ( IC ), which combined a no. of transistors & diodes together on a silicon chip, was developed.
8. Versatile :
A computer can be used in different places to perform a large number of different jobs depending on the instructions fed to it.
9. Imposition of a formal approach to working methods :
Because a computer can only work with a strict set of instructions, it identifies and imposes rigid rules for dealing with the data it is given to process.
Review Questions.
1. What is a Computer? 2. Why is a computer referred to as an electronic device? 3. Define the following terms as used in computer science. a). Data. b). Programs. c). Data processing. d). Information. 4. (a) Briefly explain the two forms of data. (b) Give THREE differences between Data and Information. 5. The speed of a computer is measured in ___________. 6. What does the term GIGO stands for? 7. List and explain 4 salient features/ properties of a computer. 8. List FIVE advantages of a computerized system over a manual system.
PARTS OF A COMPUTER.
A computer is made up of a collection of different components that are interconnected together in order to work as a single entity.
A Computer consists of the following parts/devices: -
1. The System Unit. 2. Input devices. 3. Output devices. 4. Storage devices.
System Unit.
This is the casing (unit) that houses electronic components such as the ‘ brain’ of the computer called the Central processing Unit ( CPU ) and storage devices.
The components in the System unit include: -
Central Processing Unit (CPU), which is also referred to as Processor. Motherboard. Power supply unit. Memory storage devices. Disk drives, which are used to store, record and read data.
Types of System units
There are two makes of System units:
a) Tower style system unit
This system unit is made to stand alone. They are designed to be placed on the floor.
- Tower style units have more space for expansion than the typical desktop units.
b) Desktop system units
Desktop units lie on the desk with the monitor resting on top of the system unit.
Features of the System unit.
- It houses the CPU. - It connects to all peripheral devices using ports. - It has the computer’s Power switch.
The programs & data are transferred to & from the secondary storage units to the Main memory only when they are required; hence the information is said to be online to the computer.
Examples of secondary storage devices:
- Hard disk * Floppy disks. ***** Magnetic Tapes.
- Cassette tapes. * Punched cards. * Zip disks.
- Compact disks * Digital Video Disks (DVDs).
Computer peripherals.
A computer is basically made up of a system unit and other devices connected to the system unit called Peripheral devices.
Peripheral devices are the elements (components) connected to the system unit so as to assist the computer satisfy its users.
Peripheral devices are connected to the System unit using special cables called data interface cables that carry data, programs & information to and from the processor. The cables are connected to the system unit using connectors called Ports.
Examples of peripheral devices include;
- Monitor, - Keyboard, - Mouse
- Printer. - Modem. - Speakers.
- Plotter.
Review Questions.
1. List down the components that make up a computer. 2. Clearly draw and label the main physical parts of a simple computer system. 3. What are computer peripherals? 4. (a). Name and explain the two main divisions of computer storage. (b). Give two common examples of secondary storage devices. 5. Name two output devices. 6. (a). Explain the term System unit. (b). Name some of the components found in the System unit. (c). Give three features of a computer’s System Unit. 7. Why is the screen also called a Monitor? 8. What is a Mouse in relation to computing?
DEVELOPMENT OF COMPUTERS.
HISTORY OF COMPUTING.
Before 1900, most data processing was done manually using simple tools like stones & sticks to count and keep records. Around 2000 years ago, Asian merchants came up with a special calculating tool called Abacus that could be used to calculate large figures.
An Abacus is made up of a rectangular frame and a crossbar at the middle. It is fitted with wires or strings running across from the frame to the crossbar.
How to represent a number using an Abacus.
Each bead in the lower row has a value of 1, while each bead in the upper row has a value of 5. To represent a number, the bead is moved to the crossbar. Those beads away from the crossbar represent zeros.
The Figure below represents the number 6908 (Six thousand nine hundred and eight).
After Abacus, the first machine that is usually regarded as the forerunner of modern computers was named the Analytical Engine , and was developed by an English mathematician called Charles Babbage.
In 1939, Professor Howard Aken of Horrard University designed the first computer-like machine named Mark 1. Since then, a series of advancements in electronics has occurred. With each breakthrough, the computers based on the older form of electronics have been replaced by a new “generation” of computers based on the newer form of electronics.
COMPUTER GENERATIONS.
A Computer generation is a grouped summary of the gradual developments in the computer technology. The historical events are not considered in terms of individual years, but are classified in durations (a period of more than a year).
1 ST^ Generation computers (1946 – 1956).
The 1st^ generation of computers used thousands of electronic gadgets called Vacuum tubes or Thermionic valves to store & process information.
Vacuum tube
3 RD^ Generation computers (1964 – 1979).
Used electronic devices called Integrated Circuits ( ICs ), which were made by combining thousands of transistors & diodes together on a semiconductor called a Silicon chip.
Integrated circuit
The processing speed increased to 5 Million instructions per second (5 MIPS).
The storage capacity of the computers (i.e., the RAM memory sizes) expanded to 2 MB.
They were smaller in size compared to 2nd^ generation computers.
The computers used a wide range of peripheral devices.
The computers could support more than user at the same time. They were also able to support remote communication facilities.
Magnetic disks were developed for storage purposes.
The 1st^ microcomputer was produced during this period (1974).
Examples of 3rd^ Generation computers:
IBM 360, 370; ICL 1900 Series; 8-bit Microcomputers & PDP-11 Mainframe computers.
4 TH^ Generation computers (1979 – 1989).
The 4th^ generation computers used Large Scale Integrated ( LSI ) circuits & Very Large Scale Integrated ( VLSI ) circuits. These circuits were made by compressing more tiny circuits and transistors into even smaller space of the silicon chip.
Very Large integrated circuit
The computers were small, and very fast. Their processing speeds increased to 50 Million instructions per second.
Had large storage capacity, i.e., their memory sizes expanded to several hundred Megabytes.
Memories used included Magnetic disks, Bubble memories & Optical disks.
Examples of 4th^ Generation computers:
IBM 308 and 4300; Amdahl 580 Honeywell DPS- Burroughs 7700, and the 16-bit & 32-bit microcomputers. The first microcomputer was called Apple II.
5 TH^ Generation computers (1990 – Present).
In this generation fall today’s computers.
The technologies used are Parallel architectures , 3-Dimensional circuit design & super conducting materials.
These technologies have led to the development of computers referred to as Supercomputers , which are very powerful, and have very high processing speeds. Their speeds are measured in Nanoseconds & Picoseconds.
They are able to perform parallel (or multi-processing) whereby a single task is split among a number of processors.
The memory sizes range between 1 Gigabyte & 1 Terabyte.
The computers are designed using VLSI and the Microchip technology that has given rise to the smaller computers, known as Microcomputers used today.
The computers have special instruction sets that allow them to support complex programs that mimic human intelligence often referred to as Artificial Intelligence. Such programs can help managers to make decisions and also provide critical expert services to users instead of relying on human professionals.
Review Questions.
1. Briefly describe the history of computers. 2. (a). What do you mean by computer generations? (b). Describe the FIVE generations of computers in terms of technology used and give an example of a computer developed in each generation. (c). Compare computer memory sizes during the Five computer generation periods. 3. What was the most remarkable discovery during the second computer generation? 4. (a). Technology is the basis of computer classification. Based on this, explain briefly the difference between the first three computer generations. (b). What is so peculiar in the fourth and fifth generation of computers? 5. Match the following generations of computers with the technology used to develop them.
Generation Technology
First generation A). Very Large Integrated Circuit Second generation B). Thermionic valves (Vacuum tubes) Third generation C). Transistors Fourth generation D). Integrated Circuits
6. Give four characteristics of First generation computer. 7. Write the following abbreviations in full: (a). ENIAC (b). VLSI (c). IC 8. What is Artificial Intelligence?
CLASSIFICATION OF COMPUTERS
Computers can be classified according to the following factors:
1. Physical size & processing power. 2. Purpose for which they are designed. 3. Functionality (Method/ mode of operation).
A. CLASSIFICATION ACCORDING TO PHYSICAL SIZE.
Computers can be classified into 5 main groups according to their size as: Supercomputers. Mainframe computers. Minicomputers. Microcomputers. Portable computers (Laptops, Notebooks & Palmtops).
Supercomputers.
Supercomputers are the fastest, largest, most expensive & also the most powerful computers available. They are very fast in processing. They can perform many complex calculations in a fraction of a second. Most Supercomputers use multiple processors. In this case, a single task is split among the processors for faster execution. However, all the processors are controlled by a single central processor. Supercomputers generate a lot of heat, & therefore require special cooling systems. Sometimes, the whole CPU is deeped in a tank containing liquid Fluorocarbon to provide cooling. Supercomputers are very large & heavy, and are usually kept under special environmental conditions (i.e., in a special room). They are operated by computer specialists. A Supercomputer can be operated by over 500 users at the same time.
Areas where supercomputers are used: Supercomputers are mainly used for complex scientific applications that involve many calculations & require a lot of computational power. Some of the applications that use supercomputers include; Weather forecasting. Petroleum research. Defence and weapon analysis. Aerodynamic design and simulation. Note. These tasks use large amounts of data, which need to be manipulated within a very short time. Examples of Supercomputers: CRAY T3D, NEC-500.
Mainframe computers.
Mainframes are less powerful & less expensive than supercomputers. They are big in size but smaller compared to Supercomputers. Are powerful computers with very high capacities of Main storage. They also have a large backing storage capacity. Have a very high processing speed, i.e., can process large amounts of data very quickly.
They can support a large number of peripherals of different types (can support between 5– 300 terminals).
They can handle hundreds of users at the same time, e.g., they can be operated by 200 users at a time.
Mainframe computers are general-purpose, and can handle all kinds of problems whether scientific or commercial.
Areas where mainframe computers are used:
Mainframe computers are mostly found in government departments, big organizations and companies which have large information processing needs, e.g., they are used;
In Banks & Hospitals for preparing bills, Payrolls, etc.
In communication networks such as the Internet where they act as Servers.
By Airline reservation systems where information of all the flights is stored.
Examples of Mainframes:
IBM 4381. ICL 39 Series. CDC Cyber series.
Minicomputers.
A Minicomputer is physically smaller than a mainframe. However, it can support the same peripheral devices supported by a mainframe.
A Minicomputer can support several users at a time, e.g., can be operated by 6 users at a time. Several workstations/ terminals are connected to one central minicomputer so that the users connected can share its resources (C.P.U time, storage, etc).
Minicomputers are easier to manufacture & maintain compared to mainframes. Minicomputers are cheaper than the mainframes, but more costly than the microcomputers.
They handle small amounts of data, are less powerful, & have less memory than the mainframes.
Minicomputers are slow compared to mainframe computers.
Areas where minicomputers are used:
Minicomputers are used mainly in:
Scientific laboratories & research institutions. Engineering plants/factories to control of chemical or mechanical processes. Space industry. Insurance companies & Banks for accounting purposes. Smaller organizations as Network Servers.
Example of Minicomputer:
PDP-8 built in 1965 by D igital E quipment C orporation in U.S.
Microcomputers.
Microcomputers are the PCs mostly found today in homes, schools & many small offices. They are called Personal Computers ( PCs ) because they are designed to be used by one person at a time.
They consist of very few connected units, i.e. can support very few peripheral devices (usually 1 or 2).
The data processing in microcomputers is done by a Microprocessor (a single chip containing the Arithmetic Logic unit & Control unit).
Examples of desktop computers:
1) Home computer. This is a low-cost microcomputer of limited capability designed for domestic use. It has programs that are used typically for computer games or controlling family finances.
2) Personal computer (PC). This is a microcomputer designed for independent use by an individual at work or in the home mainly for business purposes.
- A PC can support only 1 user at a time.
- PCs are mostly used in offices, schools, business premises, and at home for various applications like computer literacy, Games, Database management, Accounting, Word processing, Telecommunications, etc.
- A PC can be connected to a mini & mainframe computer so as to enable the user access the facilities offered by the larger machines.
3) Workstation. A workstation is usually a desktop computer with all the facilities but interlinked to a network. A typical workstation works in a similar way to a Personal computer. However, it is more advanced than a typical PC in the following ways: i). It is larger & more powerful than a PC. E.g., workstations use 32-bit microprocessors, while PCs use 16-bit microprocessors. ii). It has in-built capabilities for its interconnection & operation with other computers, i.e., it is fully connected to a computer network as any other computer on the network in its own right. iii). It has high resolution graphics. iv). It has a Multi-tasking operating system, i.e. it is able to run multiple applications at the same time.
An Embedded computer.
This is a computer that is within another device or system but is not accessed directly. E.g., there are embedded computers operating within Petrol pumps, Watches, Cameras & Video recorders.
B. CLASSIFICATION ACCORDING TO PURPOSE.
Digital computers can be classified further according to the tasks they perform either as: General-purpose. Special purpose Dedicated computers.
General-purpose computers.
General-purpose computers are designed to perform a wide variety of tasks. They use specifically written instructions (programs) to carry out the desired processing tasks. Example; A single computer can be used to process documents, perform calculations, process the Payroll, simulate the loading on a bridge, process Insurance policies, and play games, among others. The programs used in a general-purpose computer are exchangeable. This means that, to perform a particular task, the appropriate set of instructions required to perform that particular task are loaded into the computer memory.
E.g., if you want to play a game, the appropriate program is loaded into the computer’s memory & the computer is instructed to execute the instructions which make up the game. Examples of general-purpose computers : Mainframes, Minicomputers, Microcomputers & Laptops used in most offices & schools.
Special-purpose computer.
A special-purpose computer is designed to handle/accomplish a particular specific task only. Such computers cannot perform any other task except the one they were meant to do. Therefore, the programs which are used in a special-purpose computer are fixed (hard-wired) at the time of manufacture. For example; In a computer Network, the Front End Processor ( FEP ) is only used to control the communication of information between the various workstations and the host computer. A Special-purpose computer is dedicated to a single task; hence it can perform it quickly & very efficiently. Examples of special-purpose computers: Robots used in a manufacturing industry for production only. Mobile phones used for communication only. Calculators that carry out calculations only. Computers used in Digital watches. Computers used in Petrol pumps. Computers used in Washing machines. An Automatic pilot – a computer dedicated to the task of operating an aircraft. A Word processor – a special-purpose computer used in the production of office documents, letters, etc.
Reasons why a Mobile phone is regarded to be a computer. It is electronic. Has a screen. It has a Keypad. Has a Memory. It is programmable.
Dedicated computer.
A Dedicated computer is a general-purpose computer that is committed to some processing task; though capable of performing a variety of tasks in different application environments. E.g., the computer can be dedicated to carrying out Word processing tasks only.
C. CLASSIFICATION ACCORDING TO FUNCTIONALITY.
Usually, there are two forms of data; Digital data , and Analogue data. Computers can be classified according to the type of data they can process as either. Digital computers. Analogue computers, or Hybrid computers.
Digital computers.
This is the most commonly used type of computers. A Digital computer is a computer that operates on discrete data only. It can process both numeric & alphabetic data within the computer, e.g., 0, 1, 2, 3…, A,B,C….
A Petrol pump measures the rate of flow of Gasoline (petrol) & converts the volume delivered to 2 readings; one showing the volume & the other showing the cost. A Post-office scale converts the weight of a parcel delivered into a charge for posting. A Monitor with knobs that are rotated to increase brightness. A Television with knobs that are rotated to increase or decrease the volume. A Radio with a knob that slides in a slot to increase volume.
Hybrid computers.
Hybrid computers are designed to process both analogue & digital data. They combine both the functional capabilities of the digital and analogue computers. Hybrid computers are designed by interconnecting the elements of a digital computer & analogue computer directly into one processor, using a suitable interfacing circuitry. Hybrid computers are more expensive. Example; In a hospital Intensive Care Unit , an analogue device may be used to measure the functioning of a patient’s heart, temperature and other vital signs. These measurements may then be converted into numbers and send to a digital device, which may send an immediate signal to the nurses’ station if any abnormal readings are detected.
Comparison between a Computer and Calculator.
Computer Calculators
1. Costly due to the technology used. 2. Bigger in size. 3. Operate at very high speeds. 4. Are more accurate – they give up to over 10 decimal places of accuracy. 5. Flexible – can be used in solving any problem. 6. Work under the control of programs. 7. Support a variety of peripherals, e.g. keyboard, mouse, light pen, printer, etc. 8. Have large internal memory of several KB’s. 9. Support large Backing storage media. 10. A computer can support several people at the same time. 11. Have got telecommunication capabilities. 12. Require well-monitored environmental conditions. 1. Cheaper – they imitate simple computer technology. 2. Comparatively smaller. 3. Slower than computers. 4. Less accurate – most calculators give up to 8 dp of accuracy. 5. Mostly used for numerical calculations involving arithmetic/ mathematical operations 6. Calculators are non-programmable, but if programmable, the range is limited. 7. They only use Display units & Keyboards of limited capabilities. 8. their internal memory is very small. Most calculators only use Registers for temporary storage during calculations. 9. Some calculators have got some sort of fixed Backing store, though very limited. 10. A calculator can serve only 1 user at a time. 11. Have no telecommunication capabilities. 12. Do not require well-monitored environmental conditions.
Review Questions.
1. State three methods of classifying computers. In each case, list the different types of computers. 2. What is a Personal computer? 3. Differentiate the following types of computers. a). Supercomputer and Mainframe computer.
b). Minicomputer and a Personal computer. c). Special-purpose (dedicated) computers and General-purpose computers. d). Desktop computers and Laptop computers
4. Briefly describe terms “Analogue” and “Digital computers” as used in computer science. 5. Give three examples of Special-purpose computers. 6. Name any FOUR classes of computers based on size and complexity.
