Office Application Programs

Introduction
Computer – refers to an electronic device capable of accepting data as input and processes it under the influence of a set of instructions referred to as software/programs to produce information as output.

Data - refers the raw facts fed into the computer for processing. Data does not have any meaning to the user e.g. raw students marks fed into the computers. 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 in two states (on and off / 0 and 1).

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.

Input - This is data entry / entered via special devices known as input devices e.g Keyboard, Keypad, Mouse, Scanner, Light pen.

Processing - This is the act of manipulating data by adding, subtracting, joining, comparing, dividing and multiplying to come up with information.

Information – refers to processed data summarized in the form that the user wants. It is a function material ready to be used in the decision making process. Information makes sense to the user e.g. computed average marks.

Output - This is data extraction/extracted from the computer for the user to see. Data is extracted via output devices e.g Monitor, Speaker and Printer.

A Computer as a System – combination of different components or elements of the computer which each performs its own tasks but work together to process data into information.

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.

It is a set of instructions used to guide a computer through a process.

Accuracy:
Unlike human beings, computers are very accurate, i.e., they never make mistakes.

A computer can work for very long periods without going wrong. However, when an error occurs the computer has a number of in-built, self-checking features in their electronic components that can detect & correct such errors.

Usually errors are committed by the users entering the data to the computer, thus the saying Garbage in Garbage Out (GIGO). This means that, if you enter incorrect data into the computer and have it processed, the computer will give you misleading information.

Reliability.
The computer can be relied upon to produce the correct answer if it is given the correct instructions & supplied with the correct data.

Therefore, if you want to add two numbers, but by mistake, give the computer a “Multiply” instruction, the computer will not know that you intended to “ADD”; it will multiply the numbers supplied.

Similarly, if you give it the ADD instruction, but make a mistake and enter an incorrect data; let say, 14 & 83 instead of 14 & 38; then the computer will produce the “wrong” answer 97 instead of 52. However, note that, 97 is ‘correct’ based on the data supplied.

Therefore, the output produced by a computer is only as reliable as the instructions used & the data supplied.

Consistency:
Computers are usually consistent. This means that, given the same data & the same instructions, they will produce the same answer every time that particular process is repeated.

Storage:
­A computer is capable of storing large amounts of data or instructions in a very small space.

­A computer can store data & instructions for later use, and it can produce/ retrieve this data when required so that the user can make use of it.

­Data stored in a computer can be protected from unauthorized individuals through the use of passwords.

Diligence:
Unlike human beings, a computer can work continuously without getting tired or bored. Even if it has to do a million calculations, it will do the last one with the same speed and accuracy as the first one.

Automation:
A computer is an automatic device. This is because, once given the instructions, it is guided by these instructions and can carry on its job automatically until it is complete.

It can also perform a variety of jobs as long as there is a well-defined procedure.

Versatile:
A computer can be used in different places to perform a large number of different jobs depending on the instructions fed to it.

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.

Components 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.	Processing devices 4.	Output devices. 5.	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: -


 * 1) Central Processing Unit (CPU), which is also referred to as Processor (micro-processor).
 * 2) Motherboard.
 * 3) Power supply unit.
 * 4) storage devices.
 * 5) 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 Central processing unit (CPU)
This is the brain of the computer, and carries out all the processing within the computer. The CPU is found inside the system unit and is made up of two major parts; the Control Unit (CU) and the Arithmetic and Logic Unit (ALU), it also contains internal registers.

Input devices.
These are the devices used to enter/put data into the computer.

•	They accept data for processing & convert it into a suitable form that the computer can understand.

Examples: Keyboard, Mouse, Joysticks, Light pen, Scanner, etc.

The Keyboard
The keyboard looks like a typewriter, and has letters, numbers and other keys through which data is entered into the computer.

To enter data & instructions into the computer, the user should press the required keys.

The Mouse
It is a pointing device that enables the user to issue instructions to the computer by controlling a special mouse pointer displayed on the screen.

Output devices.
Output devices are used to give the end results of data that was entered into the computer.

­	They extract/ disseminate processed data (information) from the computer. ­	They accept data from processing devices & convert it into human sensible form.

Examples: Screens (Monitors), Printers, Graph plotters, Speakers, etc

The Monitor
It is a television like screen used for displaying output. When you type a letter or number on the keyboard, it shows up on the monitor.

Note. The monitor enables the user to monitor/track or see what is going on in the computer.

Printer
Printers are used to create permanent copies of output on paper.

Storage devices.
These are devices used to store programs & data in computers.

•	They hold data & programs until they are needed for processing. •	They also hold the results after processing.

Computer storage is divided into 2:

Primary (main) storage.
This is the storage found within the computer itself. It is used to hold data, programs & instructions required immediately (or currently being used) by the Processor.

Examples: Random Access Memory (RAM) & Read Only Memory (ROM).

Secondary (Backing) storage.
It is used by the computer to store backup information that is not needed immediately by the Processor. It is also used by the computer to supplement the computer’s main memory/ internal memory in case of mass storage purposes.

Secondary storage units provide permanent data storage facilities. They allow large quantities of information to be stored permanently on some form of magnetic media such Magnetic tapes or disks.

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.

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).

1ST 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 The tubes consumed a lot power, and generated a lot of heat during processing due to overheating.

The computers constantly broke down due to the excessive heat generated, hence were short-lived, and were not very reliable.

They also used Magnetic drum memories.

Cards were used to enter data into the computers.

Their internal memory capacity was limited. The maximum memory size was approx. 2 KB (2,000 bytes).

The computers used big physical devices in their circuitry; hence they were very large in size, i.e. the computer could occupy several office blocks. For example, ENIAC occupied an area of about 150m2 - the size of an average 3-bedroom house.

They were very slow - their speed was measured in Milliseconds. E.g., ENIAC (the earliest electronic computer) could perform 5,000 additions per second & 300 multiplications per second.

The computers were very costly - they costed millions of dollars.

Examples of 1ST Generation computers:

•	ENIAC (Electronic Numerical Integrator And Calculator) built in 1946 for use in World War II. It contained 18,000 Vacuum tubes.

•	EDVAC (Electronic Discrete Variable Automatic Computer) developed in 1945 by Dr. John Von Neumann. It was the first computer that used instructions stored in memory.

•	UNIVAC (UNIVersal Automatic Computer).

•	IBM 650. •	LEO (Lyon’s Electronic Office).

2ND Generation computers (1957 – 1963).
The 2nd generation computers used tiny, solid-state electronic devices called Transistors. The transistors were relatively smaller, more stable & reliable than vacuum tubes. Transistor

The computers consumed less power, produced less heat, were much faster, and more reliable than those made with vacuum tubes.

They used Magnetic core memories.

RAM Memory size expanded to 32 KB.

Their operation speed increased to between 200,000 – 300,000 instructions per second. Their speeds were measured in Microseconds. E.g., a computer could perform 1 million additions per second, which was comparatively higher than that of the 1st generation computers.

The computers were smaller in size & therefore, occupied less space compared to the 1st G computers.

They were less costly than the 1st G computers.

Examples of 2nd Generation computers:

•	NCR 501, IBM 300, IBM 1401, IBM 7070, IBM 7094 Series & CDC-6600 Mainframe computers. •	ATLAS LEO Mark III. •	UNIVAC 1107. •	HONEYWELL 200.

3RD 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.

4TH 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. 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-88 •	Burroughs 7700, and the 16-bit & 32-bit microcomputers. The first microcomputer was called Apple II.

5TH 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.

FACTORS THAT DETERMINE THE TYPE OF COMPUTER.
1)	Type of processor (Central processing unit – CPU)

Microcomputers use microprocessors, which are manufactured on a single chip, as their CPU. In larger computers such as supercomputers, mainframe & minicomputers, the processing is carried out by a number of separate, high-speed components instead of a single processor.

2)	Processing speed.

Every computer has a clock that drives its operations. Larger computers have faster clocks and therefore can process many instructions per second compared to small computers, which have slower clocks.

3)	Amount of Main memory (RAM).

All computers have some amount of RAM (Random Access memory), which is used to hold the instructions required to perform a task.

Larger computers have more RAM and therefore can handle large volumes of data & also support many and sophisticated programs which might require large memory sizes.

4)	Storage capacity of the Hard disk.

The storage capacity is the amount of space that is available for storing the instructions required to manipulate data.

Larger computers have higher storage capacities than microcomputers.

5)	Cost of the computer.

The cost of computers is directly related to the size. Microcomputers are less costly compared to minicomputers, mainframes or Supercomputers.

6)	Speed of Output devices.

The speed of an output device is determined by the amount of information that can be printed in a specified amount of time.

The speed of microcomputer output device is less than that of the larger computers in that:

For a microcomputer, the speed of its output device is measured by the number of characters printed per second (cps). For larger computers, their output devices are faster and their speeds are measured depending on the number of lines or pages printed per minute (lpm / ppm).

7)	Number of users who can access the computer at the same time.

Most microcomputers can support only 1, 2 or 3 users at the same time. However, they can be networked to share resources. Larger computers can support hundreds of users at the same time.

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).

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;


 * 1) 	Weather forecasting.
 * 2) 	Petroleum research.
 * 3) 	Defence and weapon analysis.
 * 4) 	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;


 * 1) 	In Banks & Hospitals for preparing bills, Payrolls, etc.
 * 2) 	In communication networks such as the Internet where they act as Servers.
 * 3) 	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 Digital Equipment Corporation 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).

Microcomputers are smaller in size & also cheaper than minicomputers. Their design is based on Very Large Scale Integration (VLSI) that confines several physical components into an IC.

They are less powerful than minicomputers & their internal memory is smaller than that of minicomputers.

Areas where microcomputers are used: Microcomputers are commonly used in:

	Training and learning institutions such as schools. 	Small business enterprises, and 	Communication centres as terminals.

Microcomputers have become very popular because of the following reasons:

1)	Are cheaper than both mini & mainframe computers. 2)	Are very fast (i.e. have high processing speeds). 3)	Small in size, hence they occupy less space in an office. 4)	Are more energy efficient (i.e., consume less power). 5)	Are more reliable than the early Mainframe computers.

Examples:

•	IBM PCs such as Apple Macintosh, Dells, Compaq, etc.

Laptops & Notebooks.

A Laptop is a PC sufficiently small & light such that a user can use it comfortably on his/her lap. It is designed to be used by placing it on the lap.

-	Laptops are very small in size & are portable. They are small enough to fit inside a briefcase; still leaving room for other items.

-	A Laptop computer operates mainly on electricity or by rechargeable batteries.

-	Laptops normally have in-built disk drives & Flat screens (Liquid Crystal Displays).

-	Can only support a limited number of peripheral devices.

-	Have limited storage capacities.

Note. The smaller computers like Laptops tend to be more expensive than Desktop computers because of the following reasons:

1)	The technology of producing smaller devices is expensive. 2)	They are convenient because they are portable. 3)	They have advanced power management capabilities (they consume less power since a laptop can operate on rechargeable batteries).

Palmtops.

Palmtops are small enough to fit in the pocket, and can be held in the palm when being used.

­	Have limited storage capacities. ­	Palmtops are mainly used as Personal Organizers, with some minimal programs for calculations, Word processing, Spreadsheets, & E-mail.

Example of a Palmtop; Personal Digital Assistant (PDA).

Desktop computer.

This is the name given to any computer designed to be used when placed on a desk in an office environment.

­	They are not portable.

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.

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.

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….

Their operation is based on 2 states, “ON” & “OFF” or on digits “1” & “0”. Therefore, any data to be manipulated by a digital computer must first be converted to digital form.

Their output is usually in form of numbers, alphabets, & symbols.

Digital computers are usually general-purpose computers; hence, they are widely used in different areas for data processing.

Most of the devices found at homes today are digital in nature. Digital computers are less accurate, i.e. may not solve all your problems since the facilities provided are generalized.

Examples:

•	A Television with a button which is pressed to increase or decrease the volume. •	Digital watches. •	Calculators. •	Microcomputers. They are said to be digital because they posses the ALU.

Analogue computers.

An Analogue computer is a computer that operates on continuous data.

They carry out their data processing by measuring the amount of change that occurs in physical attributes/quantities, such as changes in electrical voltage, speed, currents, pressure, length, temperature, humidity, etc.

An Analogue computer is usually a special-purpose device that is dedicated to a single task. For example, they are used in specialized areas such as in: ­	Scientific or engineering experiments, ­	Military weapons, ­	Controlling manufacturing processes like monitoring & regulating furnace temperatures and pressures. ­	Weather stations to record & process physical quantities, e.g., wind, cloud speed, temperature, etc.

The output from analogue computers is in form of smooth graphs produced by a plotting pen or a trace on a Cathode Ray Tube (CRT) from which the information can be read.

Note: Analogue computers usually use one characteristic, e.g. a length, to give information about another physical characteristic, such as weight.

Analogue computers are very accurate & efficient since they are dedicated to a single task.

They are very fast since most of them use multiple processors.

Examples of analogue devices:

•	The computer used to control a flight simulator for training pilots. The computer responds to the Cockpit simulator control movements made by the pilot to physically change the environment so that the pilot feels as if he were controlling an actual Aeroplane.

•	A Bathroom scale. It uses the weight of a person to move a pointer smoothly/continuously over calibrated scale, which shows the person’s weight.

•	Thermometer. It uses a volume of Mercury to show temperature. The Thermometer is calibrated to give an exact temperature reading.

•	Speedometer. In Speedometer, the rotation of the wheel is converted to a voltage, which causes a pointer to rotate over a dial calibrated in Km/h or Miles/h.

•	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.

ADVANTAGES OF USING COMPUTERS.
Computers have many advantages over other types of office and business equipments that are used for data processing functions. Some of the advantages are:


 * 1) Computers process data faster: The processing speed of a computer when measured against other devices like typewriters & calculators is far much higher.
 * 2) Computers are more accurate & reliable: Computers produce more accurate results as long as the correct instructions & data are entered.  They also have the ability to handle numbers with many decimal places.
 * 3) Computers are more efficient: A computer requires less effort to process data as compared to human beings or other machines.
 * 4) Computers can quickly and effectively store & retrieve large amounts of data.
 * 5) They are very economical when saving information, for it can conserve a lot of space.
 * 6) Computers occupy very little office space.
 * 7) Computers help to reduce paper work significantly.
 * 8) Computers are flexible: A computer can perform a variety of jobs as long as there is a well-defined procedure.
 * 9) Computers are cheap: They can be used to perform a number of organizational functions/ activities, which are meant for individual persons, hence reducing the number of employees & the costs.
 * 10) Computers enhance security & confidentiality: Data stored in a computer can be protected from unauthorized individuals.
 * 11) Have made communication easier.
 * 12) Computers produce better information: Computer output is usually tidy and error-free (accurate).
 * 13) Computers reduce the problems of data or information duplication:
 * 14) Computers can operate in risky environments, e.g. volcanic sites, dangerous chemical plants, where human life is threatened:

DISADVANTAGES OF USING COMPUTERS.

 * 1) Computers are very costly in terms of purchase & maintenance.
 * 2) Computers can only be used areas where there is source of power.
 * 3) Requires skilled manpower to operate, i.e., one has to have some knowledge so as to operate a computer.
 * 4) The records are usually kept in a form that is not visible or human-readable.  This makes it difficult to control the contents of the computer’s master file.
 * 5) A computer, like any other machine can break down.
 * 6) Information stored in computers can easily get lost due to power interruptions or machine breakdown.
 * 7) A computer doesn’t have its own intelligence, i.e., it cannot do any useful job on its own, but can only work as per the set of instructions issued.
 * 8) Installation of computers causes retraining or retrenchment of staff/ employees.
 * 9) The computer technology is changing very fast such that the already bought computers could be made obsolete/ out dated in the next few years.
 * 10) In addition, this rapid change in the computer technology makes computers & related facilities to become outdated very fast, hence posing a risk of capital loss.
 * 11) The emergence of computers has increased the rate of unemployment since they are now being used to perform the jobs, which were done by human beings.
 * 12) Computers have led to increase in computer crimes especially in Banks.  The computer criminals steal large amounts of funds belonging to various companies by transferring them out of their company accounts illegally.  In addition, they destroy vital data used in running the companies.

AREAS WHERE COMPUTERS ARE USED.
The following are some of the areas where computers are used:  Supermarkets.   Industries.
 * Supermarkets and other retail stores use computers for stock control, i.e., to help them manage their daily activities. The stock control system keeps record of what is in store, what has been sold, and what is out of stock. The Management is automatically alerted when a particular item or items are running out of stock and need to be reordered.
 * For calculating customer’s change.
 * For production of receipts.
 * It can be used as a barcode reader.

The use of computers has made Industries more productive & efficient. They are used:


 * To monitor and control industrial processes. The industries use remote controlled devices called Robots.  A Robot is a machine that works like a human being, but performs tasks that are unpleasant, dangerous, and tedious to be done by human beings.
 * For management control, i.e. to keep track of orders, bills and transactions.
 * By companies as a competitive tool. E.g., they are used to assist in defining new products & services.  They also help industries form new relationships with suppliers and therefore, enable the producers maintain a competitive edge against their competitors.
 * For advertisement purposes, which enable an industry to attract more customers.

  Banks/Insurance industries

Computers are used by Banks & Insurance industries:

 
 * To manage financial transactions. They use special cash dispensing machines called Automated Teller Machines (ATMs) to enable them provide cash deposit & withdrawal services.
 * For processing of Cheques.
 * For preparation of Payrolls.
 * For better record keeping and processing of documents.
 * To provide electronic money transfer.

LINKS

 * 1) Accounting Systems
 * 2) Access Database Creation
 * 3) Database Management Systems
 * 4) Desktop Publishing
 * 5) Excel Learning
 * 6) Graphic Software
 * 7) Presentation Software
 * 8) PowerPoint
 * 9) Spread Sheets
 * 10) Word Processing
 * 11) Review Questions