Introduction to Computer System
2.1 Description of Computer System
omputer is a device that is capable of automatically accepting (i.e. input), storing and processing data into useful information (i.e. output), at a very high speed, under the control of stored instructions (i.e. program). A computer could also be defined as a machine for manipulating data according to a list of instructions (programs). The computer is the backbone of ICT.
2.2 Parts of a Computer
If you use a desktop computer, you might already know that there isn’t any single part called the “computer.” A computer is really a system of many parts working together. The physical parts, which you can see and touch, are collectively called hardware. (Software, on the other hand, refers to the instructions, or programs, that tell the hardware what to do.)
The illustration below shows the most common hardware in a desktop computer system. Your system may look a little different, but it probably has most of these parts. A laptop computer has similar parts but combines them into a single notebook-sized package.
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2.2.1 System Unit
The system unit is the core of a computer system. Usually it’s a rectangular box placed on or underneath your desk. Inside this box are many electronic components that process information. The most important of these components is the central processing unit (CPU), or microprocessor, which acts as the “brain” of your computer. Another component is random access memory (RAM), which temporarily stores information that the CPU uses while the computer is on.
The information stored in RAM is erased when the computer is turned off. Almost every other part of your computer connects to the system unit using cables. The cables plug into specific ports (openings), typically on the back of the system unit. Hardware that is not part of the system unit is sometimes called a peripheral device or device.
2.2.2 Storage
The computer has one or more disk drives—devices that store information on a metal or plastic disk. The disk preserves the information even when your computer is turned off.
2.2.3 Hard disk drive
Computer’s hard disk drive stores information on a hard disk, a rigid platter or stack of platters with a magnetic surface. Because hard disks can hold massive amounts of information, they usually serve as your computer’s primary means of storage, holding almost all of your programs and files. The hard disk drive is normally located inside the system unit.
Figure 2b. Hard disk drive
2.2.4 CD and DVD Drives
Computers today come equipped with a CD or DVD drive, usually located on the front of the system unit. CD drives use lasers to read (retrieve) data from a CD, and many CD drives can also write Page 19 of 288 Information Communication Technology (ICT)
(record) data onto CDs. If you have a recordable disk drive, you can store copies of your files on blank CDs. You can also use a CD drive to play music CDs on your computer.
Figure 2c. CD
DVD drives can do everything that CD drives can, plus read DVDs. If you have a DVD drive, you can watch movies on your computer. Many DVD drives can record data onto blank DVDs.
2.2.5 Floppy disk drive
Floppy disk drives store information on floppy disks, also called floppies or diskettes. Compared to CDs and DVDs, floppy disks can store only a small amount of data. They also retrieve information more slowly and are more prone to damage. For these reasons, floppy disk drives are less popular than they used to be, although some computers still include them. Why are floppy disks “floppy”? Even though the outside is made of hard plastic, that’s just the sleeve. The disk inside is made of a thin, flexible vinyl material
Figure 2d. Floppy disk
.
2.2.6 Mouse
A mouse is a small device used to point to and select items on your computer screen. Although mice come in many shapes, the typical mouse does look a bit like an actual mouse. It’s small, oblong, and connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless. A mouse usually has two buttons: a primary button (usually the left button) and a secondary button. Many mice also have a wheel between the two buttons, which allows you to scroll smoothly through screens of information.
Figure 2e. Mouse
When you move the mouse with your hand, a pointer on your screen moves in the same direction. (The pointer’s appearance might change depending on where it’s positioned on your screen.) Page 21 of 288 Information Communication Technology (ICT)
When you want to select an item, you point to the item and then click (press and release) the primary button. Pointing and clicking with your mouse is the main way to interact with your computer.
2.2.7 Keyboard
A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys:
- The function keys, found on the top row, perform different functions depending on where they are used.
- The numeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly.
- The navigation keys, such as the arrow keys, allow you to move your position within a document or webpage.
Figure 2f. Keyboard
Note: We can also use your keyboard to perform many of the same tasks you can perform with a mouse.
2.2.8 Monitor
A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. Like a television screen, a computer screen can show still or moving pictures.
There are two basic types of monitors: CRT (cathode ray tube) monitors and LCD (liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter. CRT monitors, however, are generally more affordable.
Figure 2g. LCD monitors (left); CRT monitor (right)
2.2.7. Printer
A printer transfers data from a computer onto paper. You don’t need a printer to use your computer, but having one allows you to print e-mail, cards, invitations, announcements, and other materials. Many people also like being able to print their own photos at home. The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use.
Figure 2h. Inkjet printer (left); laser printer (right)
2.2.9 Speakers
Speakers are used to play sound. They may be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.
Figure 2i. Computer Speakers
2.2.9. Modem
To connect our computer to the Internet, we need a modem. A modem is a device that sends and receives computer information over a telephone line or high-speed cable. Modems are sometimes
built into the system unit, but higher-speed modems are usually separate components.
Figure 2j. Cable Modem
2.3 Advantages of Computer System
Below are some advantages of computer systems
i. Accuracy and Reliability: The results produced by a computer are extremely correct and reliable. What is often called ‗computer errors‘ are actually human mistakes; invalid data and errors are corrected easily.
ii. Speed: The speed of computer makes it the machine ideal for processing large amounts of data; e.g. accounting, banking operations etc.
iii. Storage/Memory Capability: Computer systems can store tremendous amounts of data, which can then be retrieved fast
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and efficiently. The volume of information we deal with today is far beyond what we can handle manually.
iv. Productivity: Computers are able to perform dangerous, boring, routine jobs, such as adding long list of numbers, punching holes in metal or monitoring water levels. Most workers (e.g. in banks) will appreciate increased productivity when computers are used to do their jobs.
v. Flexibility: Computer could be used for various purposes
e.g. multiprogramming, batch processing, real-time processing, data collection, bank transaction processing etc.
vi. Automatic operation: Computer performs data processing automatically under the control of internally stored programs.
vii. Configuration and adaptability: Different or suitable peripherals may be used by business organizations to suit their business processing requirements.
2.4 Disadvantages of Computer System
Some of the dis-advantages of computers are discussed below
i. Cost of initial setup may be high.
ii. Cost of maintenance may be high.
iii. Inefficient feasibility study before implementation may hamper business operations.
iv. Lack of skilled personnel may hamper computer operations and results obtained.
v. Requires regular electrical power supply.
vi. Excessive exposure to computer may result in some health problem such as poor eye sight, wrist pain, back ache, neck pain etc.
vii. Computer virus attack may infect and destroy Data/information, which will automatically affect business operations.
viii. It may lead to unemployment, because one computer can do the job of about 10 persons.
2.5 Application of Computer in Society
Computers have moved into many facets of our lives. There is virtually no area of human endeavor that computer usage has not penetrated. Though we cannot exhaust listing all the areas of application of computers, the following are some key areas of computer application:
- Science: One of the most important advantages of computers is in the field of science for research and development. The computers have played a major role in most of what we know about ourselves and the universe. The satellites, the telescopes and almost all the research tools make use of computers in some or the other way. The huge calculations required for space science, safe communication between scientists, storage of all the gathered information are some of the computer uses in science and technology.
- Medical: The important use of computers in the medical field is for research and development. The high end machines used for diagnosis and cure of many diseases are nothing but computers. For example, the Magnetic Resonance Imaging (MRI), CT scan, ultrasound devices, etc are amongst the uses of computers in hospitals. Even many surgical procedures, known as laparoscopic surgeries, need the help of computers. Web conferencing helps doctors treat people remotely.
- Education: Computer uses in the field of education are infinite. The Internet is a huge source of information. There are online universities that deliver online degrees and distance learning is spreading far and wide. Many schools and colleges have started making use of audio-visual ways of
imparting knowledge. A horde of tools that need a computer, help students in many ways.
- Banking: The banking sector has improved on fronts such as security, ease of use, etc. with the help of computers. Most of the banking operations can be done online, known as Internet banking, and you don’t have to walk up to the bank for virtually anything. You can withdraw money from ATMs and deposit money in any branch, thanks to the networking affected by the use of computers. The complete banking experience has also become safer.
- Crime Investigation: High end computer devices have ensured that justice is more effective. CCTV cameras and other computer operated security systems have reduced the amount of crime. And if it still happens there are many ways to track down the criminal in no time. Forensic science employs computers for many of its operations related to investigations.
- Entertainment: The field of entertainment has been revolutionized by computers. Animation, graphic image manipulation etc has made the entertainment experience hundred times better. Computer gaming is achieving new landmarks in terms of technology. Movie making, editing, music composition etc everything needs computers. This is only the tip of the iceberg and the uses of computers in society are many more. But then the development of computer technology has also given rise to many vices like identity theft.
- Government: The Government can use computers for the processing of immigration, tax collection/administration, keeping tracks of criminals, computing budgets and statutory allocations, Civil Service Records, computing wages, salaries, gratuities and pensions etc.
Communication: Any computer has any potential to link up with other computers through communication systems such as telephone lines or satellite. This link-up facilitates exchange of memos, reports, letters, data/information, and even having meetings among people in geographically dispersed locations.
Robotics: Robots are information machines with the manual dexterity to perform tasks too unpleasant, too dangerous, or too critical to assign to human beings. For example, robots are used in defense to perform underwater military missions; robots could be used for welding or paint-spraying in factories, and in car assembling.
Business/Commerce: Products are packaged with zebra- striped symbols (Universal Product Code {UPC}) that can be read by scanners at supermarket checkout stands to determine prices of commodities. It has become a commonplace for companies and consumers to transact business among themselves with the help of computers. It could be in form of Business-to-Business {B2B} or Business-to-Consumer {B2C}. Computers have been found useful in payroll preparation, inventory control, auditing operations, personnel records keeping, preparation of consumer utility bills, financial market transactions etc.
Energy: Energy companies use computers and geological data to locate oil, coal, natural gas and other mineral resources. Meter-readers use hand-held computers to record how much energy is used in a month in homes and businesses. Computers can analyze the fuel consumption in our cars.
2.6 Types of Computer System
Classifications of computer vary and also depend on some criterion as discussed below:
Criterion 1: Types by Data Processed
There are three (3) types of computers according to this classification criterion:
- Analog Computers: An analog computer measures and operates on data that are represented in the form of continuous variables e.g. voltage, pressure, temperature, distance, speed etc. Examples of analog computers include car speedometer, multimeter, fuel pump at filling stations etc.
- Digital Computers: A digital computer represents and processes data in discrete/numerical form, using binary system. It produces discrete output. Most computer systems we see around us today are digital computers; they are found in our homes and business environments. Some wrist watches today have digital computers embedded in them. Examples include desk calculators, adding machines, personal computers etc.
- Hybrid Computers: A hybrid computer combines the features of both analog and digital computers. It can accept continuous, discrete or both type of input. Its output could be in the form of discrete or continuous values or the combination of both. This type of computer is commonly found in highly scientific environments. Example is the electronic calculating scale used in food stores.
Criterion 2: Computer Types by physical size
In classifying computer according to physical size, there are four (4) types, namely and computers in this category are digital in nature:
- Microcomputers: Microcomputers are the smallest in size; they are the cheapest; and they have the least operational speed and memory capacity. They are made for single user and single-tasking. They are portable (i.e. they can be moved about easily), easy and simple to learn and use. The microprocessor of a microcomputer is made of integrated circuits, called chip, mounted a single circuit board. It has interfaces for input, output and storage devices. Examples include IBM Personal Computers and compatible systems, Compaq, Dell etc. Microcomputers come in different shapes and sizes: Personal Computer (PC) System: is a microcomputer designed for independent use by an individual at work or in the home mainly for business purposes. Some PCs are called Home Computers because they have limited capability designed for domestic use with programs that are typically used for computer games and controlling family finances.
- Minicomputers: Minicomputers are medium-sized, general- purpose digital computers; a bit larger than microcomputers but smaller than mainframe computers. They are multi-user (i.e. supports many users at a time) and multi-tasking (i.e. ability to perform many tasks simultaneously). Compared with microcomputers, they have larger memory size, higher processing speed, more numerous and faster input/output devices; and they are costlier. They are used in small-scale industries. Examples of mini-computer include: PDP-8, PDP-11, Honeywell-DPS6, DEC‘s VAX series, Texas instrument DS990, IBM 8100 etc.
- Mainframe computers: Mainframe computers are generally more powerful in terms of processing speed than minicomputers. They have larger memory storage memory/capacity and cost more than minicomputers. They are multi-user and multi-tasking oriented, supporting full range of programming languages, used for commercial and scientific research purposes, with sophisticated devices attached. They can access numerous terminals/workstations on a network. They use different types of peripheral devices such as tapes and disks. They are operated by well-trained
experts. Examples of mainframe computers include: NCR 8000, IBM 370,
- Super computers: Supercomputers are the largest, fastest and most expensive computers. They are often referred to as Maxi-computers. They can be seen as technological improvement on mainframe computers. They are often used in scientific environments such as in space studies and weather forecast. Examples include: CRAY-1, CRAY-2
Criterion 3: Computer Types by Purpose
There are two types of computers according to classification by purpose:
- General purpose computers: General purpose computers are designed to solve wide range of problems such as science, technology, education, business etc. Complex calculations are performed within fractions of a second and results obtained fast. Most Personal Computers (PCs) are general purpose computers.
- Special purpose computers: Special purpose computers are designed for a particular job/purpose only; to solve problems of a restricted nature. They are also called dedicated computers. Most special purpose computers are put within some other devices or systems, such that the computers are not accessed directly. These types of computers are called Embedded Computers. Examples include computers designed for use in digital watches, micro-wave oven, in petrol pumps or in weapons guidance systems.
Criterion 4: Computer Types by generations/Technology Age There are five (5) generations of computers as at date based on this criterion.
- First Generation Computers: These are computer systems manufactured during the 1940s. Their features include
- The CPU was made of vacuum tubes or thermionic valves.
- Primary memory made of magnetic drum.
- The Visual Display Unit (VDU) or monitor used cathode ray tube.
- Very bulky in size, occupied space, and very costly.
- Used machine language programming.
- Complex and cumbersome to operate.
- Generated a lot of heat.
Examples are: EDSAC, EDVAC, LEO, UNIVAC I and UNIVAC II.
- Second Generation Computers: These are computer systems manufactured during the 1950s. Their features include:
- The CPU was made of electronic transistors.
- Primary memory made of magnetic core.
- Cost less, faster, smaller and more reliable than first generation systems.
- Less complex and easier to operate compared with first generation.
- Generated less heat than first generation.
Examples: LEO Mark III, ATLAS, Honeywell 800, UNIVAC III, IBM 7000 series, etc.
- Third Generation Computers: These are computer systems manufactured around the 1960s and early 1970s.
Features:
- The CPU was made of Small Scale Integrated (SSI) Circuits, built on one Silicon Chip.
- The SSI circuits evolved to Medium Scale Integrated (MSI) circuits.
- The MSI eventually evolved into Large Scale Integrated (LSI) circuits, leading to greater degrees of integration of electrical components.
The various evolutions of IC technologies gave rise to computer systems which were smaller in size, cheaper, faster, more reliable and durable than first and second generation systems.
It was the era of minicomputers and microcomputers, resulting in higher awareness of computer technology.
The VDU were in colours.
Primary memory made of magnetic core and solid state semi-conductors.
Less complex and easier to operate compared with first and second generations.
Used high level language e.g. COBOL for operation. Examples: ICL 1900 series, IBM 360 series etc.
- Fourth Generation Computers: These are computer systems manufactured around the late 1970s to 1985. Features include the following:
- The CPU was made of Very Large Scale Integrated Circuits (VLSIC), called microchips; i.e. thousands of components in a very small space.
- There was a thin line demarcation between third and fourth generations.
- The VLSI circuits gave rise to computer systems which were more compact, cheaper, faster, more reliable and durable than first, second and third generation systems.
- It was the era of microcomputers, resulting in higher awareness of computer technology.
- Invention of microprocessors, which gave birth to pocket calculators, digital watches and the inclusion of micro hips in other devices.
- Use of fourth generation query language (4GLs).
- The VDU were in various designs – RGB, EGA, CGA, VGA colour monitors.
- Primary memory made of solid state semi-conductors.
- Less complex and easier to operate compared with first and second generations.
- Evolution of more application areas of computers.
v. Fifth Generation Computers
The research into the fifth generation computers started about 1985 and continued into 1990. The features are as follows:
- This generation is characterized by the advent of Artificial intelligence, i.e. the ability of computer system to exhibit behaviors like an intelligent person.
- Speech recognition/processing
- Parallel architecture/processing – where a computer system have hundreds of processors that could all be working on different parts of a single complex problem simultaneously.
- Pattern recognition –
- Expert system – an application program that has the capability of making judgments and decisions like a human expert in a particular field of profession. It is an interactive system that puts users through question-and-answer session to clarify issues and make recommendations, e.g. in medicine.
- Multimedia system – PC + Sound Card + Speakers + CD Drive
- Semi-conductor memory.
2.7 Social Implication Of Computer System
The society in which we live has been so profoundly affected by computers that historians refer to the present time as the information age. This is due to the ability to store and manipulate large amounts of information (data) using computers. As an information society, we must consider both the social and ethical implications of our use of computers. By ethical questions we mean asking what are the |
morally right and wrong ways to use computers and this could be explain as follows:
Ergonomics: this is the science that studies safe work environments. Many health-related issues, such as carpal tunnel syndrome and computer vision syndrome (CVS), are related to prolonged computer use.
Environmental concern: Power and paper wastes are environmental concerns associated with computer use. Suggestions for eliminating these concerns include recycling paper and printer toner cartridges and turning off monitors and printers when not in use.
Employee monitoring: Employee monitoring is an issue associated with computers in the workplace. It is legal for employers to install software programs that monitor employee computer use. As well, e- mail messages can be read without employee notification. The invasion of privacy is a serious problem associated with computers. Information: Because computers can store vast amounts of data we must decide what information is proper to store, what is improper, and who should have access to the information. Every time you use a credit card, make a phone call, withdraw money, reserve a flight, or register at school, a computer records the transaction. These records can be used to learn a great deal about you—where you have been, when you were there, and how much money was spent. Should this information be available to everyone?
Computers are also used to store information about your credit rating, which determines your ability to borrow money. If you want to buy a car and finance it at a bank, the bank first checks your credit records on a computer to determine if you have a good credit rating. If you purchase the car and then apply for automobile insurance, another computer will check to determine if you have traffic violations.
The Ethical Responsibilities of an IT Professional
IT (information technology) professional has responsibilities that relate to system reliability. System reliability involves installing and updating appropriate software, keeping hardware working and up- to-date and maintaining databases and other forms of data. Professional ethics helps a professional choose what to do when faced with a problem at work that raises a moral issue. One can certainly study what professionals do when faced with such problems, and confine the enquiry to the description. Our concern here, however, is to assist with making choices – an approach called prescriptive professional ethics.
Governments, schools, and employers rely on IT professionals to maintain their computer systems. In addition to ensuring system reliability, an IT professional must take responsibility for the ethical aspects of the career choice. The lists below are the most commonly reported behaviors IT professional which is unethical;
- Plagiarism
- Failure to protect confidential data
- Failure to share credit on a report
- Fabrication of data
- Criticize the ability/integrity of colleague for own gain
- Holding back or disguising data
- Design of sampling strategy to favor a specific outcome
- Destruction of data that contradicts desired outcome
- Deliberately not reporting an incident
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