INTRODUCTION TO COMPUTERS

Computer
A computer is an electronic device, operating under the control of instructions stored
in its own memory that can accept data (input), process the data according to
specified rules, produce information (output), and store the information for future
use.
Functions of a computer
Any digital computer carries out five functions in gross terms

i. Data input- Takes data as inputs

ii. Data and information storage-Stores data/ instructions in its memories and
stores them when required
iii. Data processing- Processes the data and converts it to useful information
iv. Information output- Generates the outputs.
v. Controls the above process.
Characteristics of Computer
i. Speed: The computer can process data very fast, at the rate of millions of
instructions per second. Some calculations that would have taken hours and
days to complete otherwise, can be completed in a few seconds using the
computer. For example, calculation and generation of salary slips of
thousands of employees of an organization, weather forecasting that requires
analysis of a large amount of data related to temperature, pressure and
humidity of various places, etc.
ii. Accuracy: Computer provides a high degree of accuracy. For example, the
computer can accurately give the result of division of any two numbers up to
10 decimal places.
iii. Diligence: When used for a longer period of time, the computer does not get
tired or fatigued. It can perform long and complex calculations with the same
speed and accuracy from the start till the end.
iv. Storage Capability: Large volumes of data and information can be stored in
the computer and also retrieved whenever required. A limited amount of data
can be stored, temporarily, in the primary memory. Secondary storage
devices like floppy disk and compact disk can store a large amount of data
permanently.
v. Versatility: Computer is versatile in nature. It can perform different types of
tasks with the same ease. At one moment you can use the computer to
prepare a letter document and in the next moment you may play music or
print a document.

Computers have several limitations too. Computer can only perform tasks that it has
been programmed to do. 10 Computer cannot do any work without instructions
from the user. It executes instructions as specified by the user and does not take its
own decisions.
Computer Hardware
Computer hardware refers to the physical(tangible) parts or components of a
computer such as the monitor, mouse, keyboard, computer data storage, hard drive
disk (HDD), system unit (graphic cards, sound cards, memory, motherboard and
chips), etc. all of which are physical objects that can be touched.
Computer Software:
The computerised instructions/Programs that operate a computer, manipulate the
data and execute particular functions or tasks.

Software is divided into two parts,

1. System software is responsible for controlling, integrating, and managing the

individual hardware components of a computer system. Generally, system
software consists of an operating system and some fundamental utilities such
as disk formatters, file managers, display managers, text editors, user
authentication (login) and management tools, and networking and device
control software.
2. Application software is used to accomplish specific tasks other than just
running the computer system. E.g. Microsoft Office, which consists of closely
integrated word processor, spreadsheet, database, etc.; or a software system,
such as a database management system, which is a collection of fundamental
programs that may provide some service to a variety of other independent
applications.
Peripheral device:

A peripheral device is an internal or external device that connects directly to a

computer or other digital device but does not contribute to the computer's primary
function, such as computing.

Since it’s not a core device for the system, the computer can still function without the
peripheral, which simply provides extra functions. However, some peripherals such
as a mouse, keyboard, or monitor tend to be pretty much fundamental to the
interaction between the user and the computer itself.

Other examples are the keyboard, mouse, external modem, external hard drives,
printers, scanners.

A peripheral device is also called a peripheral, computer peripheral, input-output

device, or I/O device.
 Components of a Computer

1. Input devices

This are devices to provide data and control signals to a computer or other
information appliance. Input device translate data from form that humans
understand to one that the computer can work with. Most common are keyboard
and mouse.
Types of Computer Input
Data -the raw facts given to the computer.

Programs- the sets of instructions that direct the computer.

Commands-special codes or key words that the user inputs to perform a task.

User response-the user's answer to the computer's question.

e. g

i. The Mouse- Used to drive Microsoft Windows (to control the cursor on the
screen.)
ii. The Keyboard-The keyboard is still the commonest way of entering
information into a computer
iii. Tracker Balls- an alternative to the traditional mouse and often used by
graphic designer
iv. Scanners-A scanner allows you to scan printed material and convert it into a
file format that may be used within the PC
v. Joysticks-Many games require a joystick for the proper playing of the game
Other examples of Input Devices: - Microphone, Graphics Tablets, Cameras, Pen
Input, Video Capture Hardware, Trackballs, Barcode reader, Digital camera
Gamepad, Electronic Whiteboard

2. Output devices
An output device is any piece of computer hardware equipment used to
communicate the results of data processing carried out by an information processing
system which converts the electronically generated information into human readable
form.

The following are examples of output devices:

1. Monitor - the monitor allows you to see the data on your computer

Basic types of monitors are

• Cathode Ray Tube (CRT).

• Liquid Crystal Displays (LCD).

• Light-emitting diode (LED).

2. Printers -Printer types:
• Laser Printer.
• Ink Jet Printer.
• Dot Matrix Printer
3. Computer Output Microfilm (COM)

4. Plotters - plotter is an output device similar to a printer, but normally allows you
to print larger images.

5. Speaker(s)- Enhances the value of educational and presentation products

6. Projector

3. Processor: Central Processing Unit (CPU)

A CPU is brain of a computer. It is responsible for all functions and processes.
Regarding computing power, the CPU is the most important element of a computer
system. The CPU is comprised of three main parts:

Arithmetic Logic Unit (ALU): Executes all arithmetic and logical operations.
Arithmetic calculations like as addition, subtraction, multiplication and division.
Logical operation like compare numbers, letters, or special characters
Control Unit (CU): controls and co-ordinates computer components.

Registers: Stores the data that is to be executed next, "very fast storage area".

4. Memory (Storage) Devices

Primary Memory: - Stores data temporarily and it is directly accessible by the
processor , it is also volatile.

1. Random Access Memory (RAM) is a memory scheme within the computer

system responsible for storing data on a temporary basis, so that it can be promptly
accessed by the processor as and when needed. It is volatile in nature, which means
that data will be erased once supply to the storage device is turned off. RAM stores
data randomly and the processor accesses these data randomly from the RAM
storage. RAM is considered "random access" because you can access any memory
cell directly if you know the row and column that intersect at that cell.

2. Read Only Memory (ROM) is a permanent form of storage. ROM stays active
regardless of whether power supply to it is turned on or off. ROM devices do not
allow data stored on them to be modified.

Secondary Memory: - Stores data and programs permanently: it’s retained after the
power is turned off .

The following are examples of secondary storage devices

i. Hard drive (HD): Also known as hard disk or hard disk drive, that store and
provides relatively quick access to large amounts of data on an
electromagnetically charged surface or set of surfaces.
ii. Optical Disk: an optical disc drive (ODD) is a disk drive that uses laser light
as part of the process of reading or writing data to or from optical discs.
Compact discs, DVDs, and Blu-ray discs are common types of optical media
which can be read and recorded by such drives.
iii. Flash Drive : This is a small portable hard drive that plugs into a USB port
and allows you to transport files between different computers. Also called a
thumb drive.
iv. Diskette (floppy disk): A small, removable, flexible mylar plastic disk
covered with a thin layer of a magnetisable substance, onto which digital data
can be recorded and stored.
v. Hard drive: Also known as hard disk or hard disk drive, that store and
provides relatively quick access to large amounts of data on an
electromagnetically charged surface or set of surfaces.
vi. Optical disk: an optical disc drive (ODD) is a disk drive that uses laser light
as part of the process of reading or writing data to or from optical discs. Also
known as a laser disk.
vii. Magnetic tape: A continuous plastic strip covered with magnetic oxide; the
tape is divided into parallel tracks onto which data may be recorded by
selectively magnetising parts of the surface, or spots, in each of the tracks. The
data can then be stored and reused.

Unit of Measurements
Storage measurements: The basic unit used in computer data storage is called a bit
(binary digit). Computers use these little bits, which are composed of ones and zeros,
to do things and talk to other computers. All your files, for instance, are kept in the
computer as binary files and translated into words and pictures by the software
(which is also ones and zeros). Computer Storage units

Bit BIT 0 or 1
1 Byte 8 bits
1 Kilobyte KB 1024 bytes
1 Megabyte MB 1024 kilobytes
1 Gigabyte GB 1024 megabytes
1 Terabyte TB 1024 gigabytes
1 Petabyte PB 1024 terabytes
1 Exabyte EB 1024 petabytes
1 Zettabyte ZB 1024 exabytes
1 Yottabyte YB 1024 zettabytes

Speed measurement: The speed of Central Processing Unit (computer speed) is

measured by gigahertz (GHz), Which represent a CPU cycle.
Advantages of using a computer
1. Speed

The speed of carrying out the given instruction logically and numerically is
incomparable between a computer and human being. Computer can perform and
give instructions in less than a millionth of a second helping us to do our tasks
within matter of seconds.

2. Accuracy

Computer calculates very accurately and computer never does mistake although we
often hear about the false results of computers. This may be due to the error in data
entry or due to poorly designed program. Since, human beings do data entry and
programming; hence, the error may make the results false. Otherwise, computer
never does mistake. It works on the principle of “Garbage In, Garbage Out”.

3. Storage
Human brain can store a piece of information to some limitation of numbers and up
to some extent of time. When he is asked to reproduce the information after a long
period, he may find himself in a difficult situation to recall the information. Human
being generally distorts the information.

4. Multitasking

Multitasking means working on multiple tasks simultaneously. Computer can

perform millions or trillions of works in one second. E. g Suppose you read an article
online and you need to write down the meanings of the words that are unfamiliar.
You, then search on Google, note down the meaning on a word file and continue
reading the article.

5. Diligence

A computer is an electronics device. It does not suffer from the human traits of lack
of concentration. So, the results will be continuously of the same standard.

6. Automation

A lot of tasks can be automated saving a lot of time. For example, instead of
manually calculating some values like mean, median of a large dataset, we just use
excel. This saves a lot of time ensuring 100% accuracy.

7. Productivity

The level of productivity gets automatically doubled as the computer can done the
work at very fast.

Disadvantages of computers

1. Online cyber crimes

As with any device, cyber-crimes occur in computers. Data stealing is one of the
major threats in the world of computers. It may occur online or via offline removable
device like that of a USB.

2. Memory without brains

Computer can store data in its memory. However, if a wrong instruction is

provided, it does not have a brain to correct the wrong instructions.

3. High cost

Computers are expensive. Even the foremost affordable computers are still very
expensive for the typical person since computers empower people.
 4. Reduction of employed opportunities

Mainly past generation wasn’t used of the pc or they need the knowledge of
computer they faced an enormous problem when computer came in field.

5. Health issues

Prolonged use of personal computers results in many health-related issues. Eye

strain, headache, back pain, etc. are some of them.

6. Slavery

A computer is a slave; it cannot execute the program by itself. It requires instructions

to execute the program and generate information. Thus, we see that the computer
cannot do anything by itself. It has a relationship of master and slave.