Welcome To Myschoollibrary! We welcome you also to the computer segment of our classes. In our computer studies lesson today, we will be taking you through an overview of the computer system. Do have a pleasant moment studying with us.

Lesson Note

Subject: Computer studies

Topic: Overview Of Computer System

Period: Lesson One
Learning Objectives: By the end of the lesson, the learners should be able to:

  1. Define the term computer.
  2. Classify computer into hardware and software.
  3. List examples of hardware and software.
  4. State the characteristics of a computer.
  5. Recognise a computer set.


The term ‘computer’ is derived from the word ‘compute’ which means to calculate. A computer is an electronic machine, devised for performing calculations and controlling operations that can be expressed either in logical or numerical terms. In simple words, a computer is an electronic device that performs mathematical and non-mathematical operations with the help of instructions to process the data to achieve desired results. Although the application domain of a computer depends totally on human creativity and imagination, it covers a huge area of applications including education, industries, government, medicine, scientific research, law and even music and arts.
Computer is a programmable machine that can store, retrieve, and process data. This means it can execute a programmed list of instructions and respond to new instructions that it is given.
It can also be defined as an electronic device designed to accept data, perform prescribed mathematical and logical operations at high speed, and display the results of those operations.
Today’s computers have at least one CPU that performs most calculations and includes a main memory, a control unit, and an arithmetic logic unit. A computer is a device that accepts information ( in the form of digitalized data ) and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed.

Characteristics Of Computers

There are certain qualities possessed by the computer that tend to make it advantageous over other means of data processing. Some of these qualities are:
(a) High Speed : Computers are electronic devices and as such, can operate at the speed of electricity. This makes the computer so fast in operation that in a matter of seconds, the computer can accomplish what will take human beings days to do. The computers process data at an extremely fast rate, i.e at millions or billions of instructions per second. In a few seconds, a computer can perform a huge task that a normal human being may take days or even years to complete. The speed of a computer is measured in megahertz (MHz), that is, one million instructions per second.
(b) Accuracy : Computers do not make mistakes in so far as they are accurately programmed and are not faulty in terms of components. Because computers can operate error-free, they can be trusted to produce accurate results, which is very vital to the users. Besides being efficient, the computers are also very accurate. The level of accuracy depends on the instructions and the type of machines being used. Since we know that the computer is capable of doing only what it is instructed to do, faulty instructions for processing the data automatically lead to faulty results. The faulty results due to faulty instructions or incorrect input data are known as GIGO, that is, ” Garbage In Garbage Out”.
(c) Reliability : Generally, reliability is the measurement of the performance of a computer, which is measured against some predetermined standard for operation without any failure. The major reason behind the reliability of the computers is that, at hardware level, it does not require any human intervention between it’s processing operations. Moreover, computers have built-in diagnostic capabilities, which help in continuous monitoring of the system.
(d) Mass Storage Capability : Computers can store very large amounts of data for long periods of time. Computers can store large amounts of data and it can recall the required information almost instantaneously. The memory of the computer is relatively small and it can hold only a certain amount of information. Therefore, the data are stored on storage devices such as magnetic tape or disks. The data from these devices can be accessed and brought into the main memory of the computer, as and when required, for processing.
(e) Versatility : Computers are quite versatile in nature. They can perform multiple tasks simultaneously with equal ease. They can be used in many fields. Some areas in which the computer can be used include payroll, exam marking, accounting, military, teaching and learning, designing and manufacturing, entertainment, airline seat reservation, etc. For example, at one moment it can be used to prepare a letter, at the other moment it can be used to play music and in between one can print a document as well. All this work is possible by changing the program ( sequence of instructions for computers ).
(f) Diligence : Computer, being a machine, does not suffer from the human traits of tiredness and lack of concentration. If four million calculations have to be performed, then the computer will perform the last four-millionth calculation with the same accuracy and speed as the first calculation.
(g) Resource Sharing : In the initial stages of development, computer used to be an isolated machine. With the tremendous growth in computer technologies, today’s computers have the capability to connect with each other. This has made the sharing of costly resources like printers possible. Apart from device sharing, data and information can also be shared among groups of computers, thus creating a large information and knowledge base.
(h) Security : Because data and information in computer systems are stored in machine-readable forms, they are protected to some extent from people who have no access to the computer by the use of passwords or some other form of identification. Thus, we can say that the computer provides a measure of security for data and information stored in it.

Advantages Of Computers

There are many advantages of using computers in larger resource centres, or smaller resource centres that have a large number of periodicals, serve many users based at a distance, or provide a wide variety of services. The main advantages of computers are:
(i) more information sources
(ii) more opportunities for cooperation and networking
(iii) increased access to the information in the resource center
(iv) increased efficiency
(v) more services

(A) More Information Sources: A computer with a CD-ROM drive can provide access to materials stored on a CD-ROM, including databases ( containing descriptions of materials ) and full-text ( complete ) materials. A computer linked to a modem can provide access to information available via e-mail and other Internet services, such as electronic newsletters and websites.
(B) More Opportunities For Cooperation And Networking: A computer linked to a modem makes it easier to communicate with the other resource centres, via e-mail. Sharing information among different resource centres can improve users’ access to information and cut down duplication of effort.
(C) Increased Access To The Information Stored In The Resource Centre: The main way to search for materials using a catalogue card system is by author, title, and a limited number of keywords. To add more keywords or other details would require cards. This would require more work, and the catalogue would become larger and more difficult to keep up-to-date. A computer database enables materials to be searched using keywords, or using other details such as series titles, publisher, year published or individual words from a title if the full title is not known, all without extra work.
(D) Increased Efficiency: Information stored on a computer database can be used for different purposes. For example, details of materials entered onto a database when ordering them can be used for a catalogue, simply by adding classification numbers and keywords. The same records can be used to produce current awareness bulletins or resource lists.
(E) More Services: A computer can be used to ‘repackage’ information held on a database, in the form of directories, resource lists or current awareness bulletins. Information held on the computer or available via the Internet can be adapted to produce locally relevant materials.

Disadvantages Of Computer

(a) The computer can only do what you tell it to do: Do not expect the computer to give you something which you never tells it to do. It will only give you what you ask it.
(b) It cannot generate information on its own: Your computer depends on you. It will not run unless you operate it. In the same way, it cannot give you information you need if you do not feed it with the necessary data.
(c) The computer cannot correct wrong instructions: If you give the computer wrong instructions, it will not be able to do anything to correct it. It will only stop functioning. Then, the computer will depend on you to correct it’s mistake.
(d) The computer will give you wrong information if you feed it with wrong data: The computer cannot distinguish between correct data and wrong data. Thus, if you feed your computer with wrong data, it will result in the computer giving you wrong information.

Classification Of Computers

Computers are available in different sizes and types. Some computers are designed to be used by a single user only, whereas some computers can handle the needs of many users simultaneously. Computers also differ based on their data-processing abilities. In general, the computers can be classified according to purpose, data handling and functionality.

Classification According To Purpose

Computers are designed for different purposes. They can be used for either general or specific purposes.

General-purpose Computers

A general-purpose computer, as the name suggests, is designed to perform a range of tasks. These computers have the ability to store numerous programs. These machines can be used for various applications, ranging from scientific to business-purpose applications. Even though such computers are versatile, they generally lack speed and efficiency. The computers used in schools and homes are general-purpose computers.

Specific-purpose Computers

These computers are designed to handle a specific problem or to perform a single specific task. A set of instructions for the specific task is built into the machine. Hence, they cannot be used for other applications unless their circuits are redesigned, that is, they lack versatility. However, being designed for specific tasks, they can provide the result very quickly and efficiently. These computers are used for airline reservations, satellite tracking and air traffic control.

Classification According To Type Of Data-handling Techniques

Different types of computers process the data in different manner. According to the basic Data-handling techniques, computers can be classified into three categories: analog, digital and hybrid.
(a) Analog Computers: A computing machine that operates on data in the form of continuously variable physical quantities is known as analog computer. These are different from a digital computer because an analog computer can perform several mathematical operations simultaneously. It uses continuous variables for mathematical operations and utilizes mechanical or electrical energy.
These computers do not deal directly with the numbers. They measure continuous physical magnitudes ( eg temperature, pressure, and voltage ), which are analogous to the numbers under consideration. For example, the petrol pump may have an analog computer that converts the flow of pumped petrol into two measurements: the quantity of petrol and the price of that quantity.
Analog computers are used for scientific and engineering purposes. The main feature of analog computers is that they are very fast in operation as all the calculations are done in ‘parallel mode’. It is very easy to get graphical results directly using analog computer.
However the accuracy of analog computer is less.

(b) Digital Computers: They use digital circuits and are designed to operate on two states, namely bits 0 and 1. They are analogous to states ON and OFF. Data on these computers is represented as a series of 0s and 1s. Digital computers are suitable for complex computation and have higher processing speeds. They are programmable. Digital Computers are either general purpose computers or special purpose ones. General purpose computers, as their name suggests, are designed for general use while specific purpose computers are meant for specific use.
A computer that operates with information, numerical or otherwise, represented in a digital form is known as digital computer. Such computers process data (including text, sound, graphics and video) into a digital value (in 0s and 1s). In digital computers, analog quantities must be converted into digital quantity before processing. In this case, the output will also be digital. If analog output is desired, the digital output has to be converted into analog quantity. The components, which perform these conversions, are the essential parts or peripherals of the digital computer.
Digital computers can give the results with more accuracy and at a faster rate.
The accuracy of such computers is limited only by the size of their registers and memory. The desktop PC is a classic example of digital computer.

(c) Hybrid Computers: These computers are a combination of both digital and analog computers. In this type of computers, the digital segments perform process control by conversion of analog signals to digital ones. Hybrid computer incorporates the measuring feature of an analog computer and counting feature of a digital computer. For computational purposes, these computers use the analog components and for the storage of intermediate results, digital memories are used. To bind the powers of analog and digital techniques, that is, analog to digital and digital to analog, the hybrid computers comprehensively use converters. Such computers are broadly used in scientific applications, various fields of engineering and industrial control processes.

Classification According To Functionality

Based on physical size, performance and application areas, the computers are generally classified into four major categories: micro, mini, mainframe and super computers.
(a) Micro Computers: A micro computer is a small, low-cost digital computer, which usually consists of a micro-processor, a storage unit, an input channel and an output channel, all of which may be on one chip inserted into one or several PC boards.
A computer with a micro-processor and it’s central processing unit is known as a microcomputer. They do not occupy space as much as mainframes. When supplemented with a keyboard and a mouse, microcomputers can be called personal computers. A monitor, a keyboard and other similar input-output devices, computer memory in the form of a RAM and a power supply unit come packaged in a microcomputer. These computers can fit on desks or tables and prove to be the best choice for single-user tasks. IBM-PC Pentium 100, IBM-PC Pentium 200 and Apple Macintosh are some of the examples of micro computers. Micro Computers include desktop, laptop, and hand-held models such as personal digital assistants (PDAs).

Desktop: A desktop computer or personal computer (PC) is the most common type of micro computer. A desktop is intended to be used on a single location. The spare parts of a desktop computer are readily available at a relatively lower costs. Power consumption is not as critical as that in laptops. Desktops are widely popular for daily use in the workplace and households.

A laptop is a portable computer that a user can carry around. Since the laptop resembles a notebook, it is also known as notebooks. Similar in operation to desktops, laptop computers are miniaturized and optimized for mobile use. Laptops run on a single battery or an external adapter that charges the computer batteries. They are enabled with an inbuilt keyboard, touch pad acting as a mouse and a liquid crystal display. Their portability and capacity to operate on battery power have proven to be of great help to mobile users. The biggest advantage of laptops is that they are lightweight and can be used anywhere and at any time, especially while travelling.

They fall in the category of laptops, but are inexpensive and relatively smaller in size. They had a smaller feature set and lesser capacities in comparison to regular laptops, at the time they came into the market. But with passing time, netbooks too began featuring almost everything that notebooks had.
A Palmtop or Handheld PC: Is a very small microcomputer that also sacrifices power for small size and portability. These devices typically look more like a tiny laptop than a PDA, with a flip-up screen and small keyboard. They may use Windows CE or similar operating system for handheld devices.

Personal Digital Assistants (PDAs): It is a handheld computer and popularly known as a palmtop. It has a touch screen and a memory card for storage of data. PDAs can also be used as portable audio players, web browsers and smartphones. Most of them can access the Internet by means of Bluetooth or Wi-Fi communication.
Servers: They are computers designed to provide services to client machines in a computer network. They have larger storage capacities and powerful processors. Running on them are programs that serve client requests and allocate resources like memory and time to client machines. Usually they are very large in size, as they have large processors and many hard drives. They are designed to be fail-safe and resistant to crash.
Wearable Computers: A record-setting step in the evolution of computers was the creation of wearable computers. These computers can be worn on the body and are often used in the study of behavior modeling and human health. Military and health professionals have incorporated wearable computers into their daily routine, as part of their studies. When the users’ hands and sensory organs are engaged in other activities, wearable computers are of great help in tracking human actions. Wearable computers do not have to be turned on and off. They remain in operation without user intervention.
Tablet Computers: Tablets are mobile computers that are very handy to use. They use the touch screen technology. Tablets come with an onscreen keyboard or use a stylus or a digital pen. Apple’s iPad redefined the class of tablet computers.

(b) Mainframe: A mainframe computer is a large, powerful computer that handles the processing for many users simultaneously (up to several hundred users). The name mainframe originated after minicomputers appeared in the 1960’s to distinguish the larger systems from the smaller minicomputers.
Users connect to the mainframe using terminals and submit their tasks for processing by the mainframe. A terminal is a device that has a screen and keyboard for input and output, but it does not do it’s own processing (they are also called dumb terminals since they can’t process data on their own). The processing power of the mainframe is time-shared between all of the users. (Note that a personal computer may be used to “emulate” a dumb terminal to connect to a mainframe or minicomputer; you run a program on the PC that pretends to be a dumb terminal).
Mainframes typically cost several hundred thousands dollars. They are used in situations where a company wants the processing power and information storage in a centralized location. Mainframes are also now being used as high-capacity server computers for networks with many client workstations or for serving files over the Internet.

(c) Mini Computer: A minicomputer is a multi-user computer that is less powerful than a mainframe. This class of computers became available in the 1960’s when large scale integrated circuits made it possible to build a computer much cheaper than the then existing mainframes.

(d) Supercomputer: A supercomputer is mainframe computer that has been optimized for speed and processing power. The most famous series of supercomputers were designed by the company founded and named after Seymour Cray. The Cray-1 was built in the 1976 and installed at Los Alamos National Laboratory. Supercomputers are used for extremely calculation-intensive tasks such as simulating nuclear bomb detonations, aerodynamic flows, and global weather patterns.

Done studying? See lesson two of this lesson

Take a quick test for this lesson

Objective Questions
1. ____ is the science that attempts to produce machines that display the same type of intelligence that human do.
(a) Nanoscience
(b) Nanotechnology
(c) Simulation
(d) Artificial Intelligence
2. The components that process data are located in the ____
(a) Input devices
(b) Output devices
(c) System unit
(d) Storage component
3. Smaller and less expensive PC based servers are replacing ____ in many businesses
(a) Super computers
(b) Clients
(c) Laptops
(d) Mainframes
4. ____ are specially designed computers that perform complex calculations extremely rapidly
(a) Servers
(b) Super computers
(c) Laptops
(d) Mainframe
5. Which of the following is the correct order of the four major functions of a computer
(a) Process–Output–Input–Storage
(b) Input–Output–Process–Storage
(c) Process–Storage–Input–Output
(d) Input–Process–Output–Storage
6. A ____ computer (also referred to as a laptop), is a small, lightweight personal computer that incorporates the screen, the keyboard, storage, and processing components into a single portable unit
(a) Notebook
(b) Journal
(c) Diary
(d) Briefcase
7. A ____ is a device that not only provides surge protection, but also furnishes your computer with battery backup power during a power outage
(a) Surge strip
(b) USB
(c) UPS
(d) Battery strip
8. The term ____ designates equipment that might be added to a computer system to enhance it’s functionality
(a) Digital device
(b) System add-on
(c) Disk pack
(d) Peripheral device
9. A ____ computer is a large and expensive computer capable of simultaneously processing data for hundreds of users
(a) Server
(b) Mainframe
(c) Desktop
(d) Tablet
10. What are the advantages and disadvantages of computer?
11. What are the characteristics of computer?

Questions answered correctly? Kudos!!

Do stay connected to Myschoollibrary for update lessons!

We are are here to make learning easy for you as you stay home for the pandemic. Stay safe, study hard, success awaits you!