Are well adapted for accounting, word processing, database management applications etc. in organisations.
Examples of minicomputers include Control Data's CDC 160A and CDC 1700, DEC PDP and VAX series, Data General Nova Hewlett-Packard HP 3000 series, HP 2100 series, HP1000 series, Honeywell-Bull DPS 6/DPS 6000 series, IBM midrange computers, Interdata 7/32 and 8/32, Varian 620 100 series.
(4) MICRO COMPUTERS
They are the smallest, cheapest and less powerful than any other type of computer.
They are called microcomputers because their CPU is called a micro-processor which is very small compared to that of mini, main frame or super computers.
Micro computers are also called Personal Computers (PC) because they are designed to be used by one person at a time.
They are mainly used for teaching and learning institutions, small businesses and communication centres etc.
Technological advancement with time has seen the development of smaller micro- computers that have greater processing speed and power.
NB: A microprocessor is a single chip containing the Arithmetic Logic Unit and Control unit. The microprocessor does the data processing in microcomputers.
Types of micro computers
1. Desktop computers - they are not portable and they are designed to be placed on top of an office desk.
2. Laptop computers - they are portable like a briefcase and they are designed to be used by placing it on the lap hence, its name.
Laptops are small in size and are portable. They are small enough to fit inside a briefcase and still leave room for other items.
Laptop computers operate mainly on electricity or on rechargeable batteries.
Laptop computers normally have in-built disk drive and flat screen (Liquid crystal display LCD)
Can support a limited number of peripheral devices and have limited storage capacities
NB: The smaller computers like laptops tend to be more expensive than Desktop computers since:
(i) The technology of producing smaller devices is expensive.
(ii) They have advanced power management capabilities (they consume less power since a laptop can operate on rechargeable batteries)
3. Palmtop computers - they are small enough to fit in the pocket and can be held in the palm while being used e.g. Personal Digital Assistant (PDA).
Have limited storage capacities.
Are mainly used as Personal Organizers, with some minimal programs e.g. word processing, spreadsheets, e-mail etc.
Notebook
A notebook computer is an extremely lightweight battery or AC powered personal computer, generally smaller than a briefcase that can easily be transported and conveniently used in temporary spaces such as on airplanes, in libraries, temporary offices, and at meetings.
Areas where microcomputers are used
Training and learning institutions such as schools
Small business enterprises
In communication centres as terminals
NB: Microcomputers are very popular because they are:
(i) cheaper than both mini and mainframe computers
(ii) are very fast i.e. have high processing speeds
(iii) are small in size hence do not occupy much space in an office
(iv) are energy efficient in that they do not consume a lot of power
Examples of minicomputers include IBM PCs such as Apple Macintosh, Dell, Compaq, HP etc. 6
(II) CLASSIFICATION OF COMPUTERS ACCORDING TO PURPOSE
Computers can also be classified according to the tasks they perform.
(a) General purpose computers
These are computers designed to perform a variety of tasks when installed with appropriate programs. e.g. a desktop computer may be used in document processing, accounting etc., a smart phone can be used in communicating, surfing/browsing the internet, playing games, etc.
(b) Special purpose computers
These are computers developed in a way that allows them to perform a specific task.
NB: these computers cannot perform any other task except the one they have been set up to do. e.g.
Robots- used in manufacturing industry and war.
Remote control unit.
Calculators- to carry out calculations only.
Mobile phones- when used in communication only etc.
(advantage of using special purpose computers is that they are very efficient and very fast)
(c) Dedicated computers
These are mainly General purpose computers that have been dedicated to perform a particular task. e.g. a desktop computer dedicated to document processing, spreadsheets, databases, accounting etc.
III. CLASSIFICATION OF COMPUTERS ACCORDING TO FUNCTIONALITY
Computers can be classified according to the type of data they process.
Hence, analog computers, digital computers and hybrid computers.
Analog Computers
They process data which is continuous in nature.
They carry out data processing by measuring the amount of change that occurs in physical attributes/quantities such as changes in electrical voltage, speed, electric current, pressure, temperature, humidity, length etc.
They are used in such specialized areas as:
Weather stations to record and process physical quantities such as wind speed, cloud speed, temperature etc.
Military weapons control
Process control as in manufacturing processes whereby there is monitoring and regulation of temperature, pressure etc.
Scientific and engineering experiments etc.
Examples of analogue devices include:
The computers used to control flight simulators 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/she is controlling an actual aircraft
Bathroom scale. (Uses the weight of a person to move a pointer smoothly/continuously over a scale thereby indicating the user’s weight)
Car speedometer. (The rotation of the wheel is converted to a voltage which causes a pointer to rotate over a scale calibrated in kph or mph)
Petrol pump. (Measures the rate of flow of petrol and converts the volume delivered into two readings i.e. the volume of fuel and the cost)
A radio with a knob that slides in a slot to increase/decrease volume.
A television with knobs that are rotated to increase/decrease brightness and/or volume.
Digital computers
They process data which is discrete in nature.
Their operation is based on two states i.e. on and off, or digits 1 and 0. Any data to be manipulated by a digital computer must first be converted to digital form. However, the output is usually in the form of numbers, alphabets and symbols.
Digital signal
Most of the devices nowadays in homes and offices are digital in nature.
Examples of digital devices include:
Calculators
Microcomputers
Digital watches
Television with volume control in the form of a button which is pressed in order to increase/decrease volume. Etc.
Hybrid computers
Are designed to process both analogue and digital data.
Are designed by interconnecting the elements of a digital computer and an analogue computer directly into one processer using suitable circuitry.
e.g. In a hospital’s Intensive Care Unit (ICU), analog devices may be used to measure the functioning of a patient’s heart, temperature, blood pressure etc. and then the measurements are converted into numbers and sent to a digital device, which could then send a signal immediately to the nurses’ station if any abnormal readings are detected.
Areas where computer are used / Application Areas of Computers
Supermarkets
Used in:
Stock control where the stock control system keeps account of what is in the store, what is to be sold and what is out of stock.
Payment of bills
Making and keeping accounting records
Surveillance of shoppers
Offices
Most modern offices functions have been automated for faster message distribution and processing.
Banks
Efficiency and speed has increased in banks due to better keeping and document processing by computers.
Special Cash Dispensing Machines called ATMs (Automatic Teller Machines) have enabled automated cash deposits and withdrawal services.
Industry Commerce
Computers are being used to monitor and control industrial processes.
Remote controlled devices like robots are also being used to perform human tasks which are too dangerous, complex, unpleasant and tedious to human beings.
Health care
Computers are used:
To keep patients records in order to provide easy access to all patients’ treatment and diagnosis. A doctor in need of specialized opinions can easily retrieve such information from computer storage memory.
For electro-cardiogram screening and motoring for patients’ diagnosis.
Enable access to foreign consultations and expertise / labor easily which would otherwise have not been possible due to high traveling costs
To carry out computerized diagnosis
To carry out computerized surgery
Transport and Communication industry
Computers are used:
To monitor vehicle traffic in busy towns, aircrafts navigation and to make reservations.
In telephone exchange to switch incoming and out going calls.
to coordinate the movement of their wagons and goods at Railway corporations
to control air traffic and surveillance of air space
to make air ticket reservations
Education and research
Computers are widely used:
In teaching and learning processes and in research institutions. E.g. long distance learning, open university concept
Learning and teaching using computers is referred to as Computer Aided Learning (CAL) and Computer Aided Teaching (CAT).
In aviation for training pilots through simulation i.e. computers are used to physically change the environment so that the pilot feels as if he controlling an actual aircraft.
Engineers and architects use computers to design test and re-design.
By scientists to analyze experimental data
For manned and unmanned space exploration
Police and defense
Computers are widely used today in fighting crime through:
Police keep record of finger-prints which are automatically analyzed by computers.
Computer-based face recognition and scene monitoring help police force to arrest traffic offenders and criminals.
In defense, computers are used:
in electronic news gathering
efficient communication
detection and tracking of targets,
radar systems
warning systems,
Military laser and missile systems.
Home and leisure
At home computers are used:
For shopping purposes because they provide shopping lists as well as electronic money transfer facilities
