BASICS IN COMPUTER APPLICATIONS - UNIT I

COMPUTER
APPLICATIONS IN
ECONOMICS

PERIPHERAL DEVICE
A peripheral device is a device that either enters information into a computer system or receives information from the computer
system. The normal workflow of a computer system is the following.
It receives data and commands from the user, processes the data according to the given commands, presents the processed data
to the user, and stores or prints the processed data if the user gives a command to save or print.
Except for the components that process the given data, all other components of a computer system are known as peripheral
devices.
In simple words, if a hardware component is not part of the core components and is used either to put information into the
computer system or to get information from the computer system, then it is a peripheral device. The core components of a
computer system are the components that control the computer system and process the data.
A computer system can function without peripheral devices but it cannot function without core components. Examples of core
components are CPU, motherboard, power supply, RAM, and ROM. Keyboard, mouse, monitor, printer, scanner, and USB
drive are examples of peripheral devices.

Peripheral devices are classified into three types. These types are input devices, output devices, and input/output devices.
An input device inserts data or commands into the computer system. A keyboard, mouse, scanner, barcode reader,
digital pen, webcam, microphone are some examples of input devices.
An output device receives the processed data from the computer system and presents that data to the user. A monitor,
printer, speaker, headphone, and projector are some examples of output devices.
An input/output device can perform both input and output functions. A hard drive, USB drive, memory card, tape drive, and
NIC are some examples of input/output devices.
TYPES OF PERIPHERAL DEVICES

Examples of peripheral devices
So far we have discussed what a peripheral device is and how many types of peripheral device are. Now, let's discuss some most
common peripheral devices and their functions.
1. Keyboard
A keyboard is the most common and important input device. It allows the user to enter letters, numbers, and symbols. When a
user presses a key on a keyboard, the keyboard sends a unique signal to the computer. The processing unit of the computer
receives the signal and translates the signal to know which key is pressed.
2. Mouse
A mouse is another important input device. It uses point-and-click technology to interact with the system. Most mice have two
buttons and a scroll wheel between them. To track motion, a ball was used in older mice. Modern mice use laser light to track
motion.
3. Webcam
A webcam is a popular input device. It captures live videos and photos. Usually, it is inbuilt on laptops and tablets. Mostly, it is
used for video calls and live presentations.
4. Scanner
A scanner is another popular input device. It is used to scan documents. Normally, it is used to save and use a soft copy of the
document.

5. Monitor
A monitor is one of the most important output devices. It receives output from the processing unit and displays that output. The
output displayed on the monitor is temporary. Because of this, the output displayed on the monitor is called the soft copy of the
output. To make it permanent, you have to store it on other output devices.
6. Printer
A printer is another important output device. It prints the given output. After printing, the output is permanently stored on the
paper. Because of this, the output printed on the paper is called the hard copy of the output. There are mainly three types of
printers: dot-matrix, inkjet, and laser. A dot printer uses pins and an ink-coated ribbon for printing. An inkjet printer uses liquid
ink for printing while a laser printer uses a laser toner for printing.
7. Speaker
A speaker is a popular output device. It plays the audio output signals. Laptops and tablets have inbuilt speakers. On desktop
computers, they can be attached via ports.

8. Hard disk
A hard disk is the most important input/output device. It provides both input and output functionalities. When a computer reads
data from the hard disk, the hard disk provides input functionality. When the computer stores data on the hard disk, the hard
disk provides output functionality.
9. USB drive
USB drives are another popular input/output device. They are compact and small. They are mostly used to transfer data
between computers that are not connected. When you transfer data from a computer to the USB drive, the USB drive provides
output functionality. When you transfer data from a USB drive to the computer, the USB drive provides input functionality.
10. NIC
NIC stands for the network interface card. A NIC is an input/output device. A computer uses a NIC to connect the network.
When the computer sends data to the network, it uses the output function of the NIC. When the computer receives data from the
network, it uses the input function of the NIC.

ADVANTAGES DISADVANTAGES
1.JOYSTICK:-Easy to learn to use. 1.Directions in simple joysticks are limited
2.REMOTE CONTROL:- Each function can have its
own button making them very simple to use.
2.They cannot be used to control anything other than
the device they were designed for.
3.DIGITAL CAMERA:- No film is needed and
unwanted images can be deleted straight away.
3.Images often have to be compressed to avoid using up
too much expensive.
4.HEADPHONE:- Easy to use and keep. 4.It required digital sound signal to convert.
5.STORAGE DEVICE:- Very fast to access the data
and cheap to buy.
5.Saved data are deleted ,if device fails.

COMPONENTS OF COMPUTER
Introduction
Computer System is an electronic data processing device which does the following:
● Accept and store an input data.
● Process the data input.
● And output the processed data in required format.

A computer system consists of following important components.
All types of computer follows a same basic logical structure and perform the following five basic operations for converting
raw input data into information useful to their users

Input Unit
This unit contains devices with the help of which we enter data into computer. This unit makes link between user and computer.
It allows people to enter information to computers. An input unit consist any hardware device that sends data to the computer The
input unit (devices) translate the human being information into the form understandable by computer.
Example: Keyboard, Mouse, Touch screen, OMR,OCR, Light pen, Scanner
CPU (Central Processing Unit)
CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate
results and instructions (program).It controls the operation of all parts of computer.
CPU itself has following three components
● ALU(Arithmetic Logic Unit)
● Memory Unit
● Control Unit

Memory Unit: (Storage Unit)
This unit can store instruction, data and intermediate results. This unit supplies information to the other units of the
computer when needed. It is also known as internal storage unit or main memory or primary storage or Random access
memory (RAM).
Its size affects speed, power and capability. There are primary memory and secondary memory two types of memories
in the computer. Functions of Memory Unit are:
● It stores all the data to be processed and the instructions required for processing.
● It stores intermediate results of processing.
● It stores final results of processing before these results are released to an output device.
● All inputs and outputs are transmitted through main memory.

Control Unit
This unit controls the operations of all parts of computer. It does not carry out any actual data
processing operations.
Functions of this unit are
● It is responsible for controlling the transfer of data and instructions among other units of
a computer.
● It manages and coordinates all the units of the computer.
● It obtains the instructions from the memory, interprets them and directs the operation of
the computer.
● It communicates with Input/ Output devices for transfer of data or results from storage.
● It does not process or store data.

ALU (Arithmetic Logic Unit)
This unit consists of two subsections namely
● Arithmetic section
● Logic Section
Arithmetic section
Function of Arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. All
complex operations are done by making repetitive use of above operations.
Logic Section
Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data.
Output Unit
Output unit consists of devices with the help of which we get the information from computer.It Allows people to receive
information from computers. An output unit (devices) is any peripheral that receives or displays output from a computer. This
unit is a link between computer and users. Output devices translate the computer’s output into the form understandable by
users.Example: Monitor, Printer, LCD, Plasma Display, Plotters

INPUT AND OUTPUT DEVICES
Input Devices
A device that can be used to insert data into a computer system is called as input device.
It allows people to supply information to computers without any input devices, a computer would only be a display device and not allow
users to interact with it. Examples of input devices include keyboards, mouse, scanners, digital cameras and Light pen, joysticks, Touch-
screen, OMR, OBR,OCR.
1.Keyboard
Most common and very popular input device is keyboard. The keyboard helps in inputting the data to the computer. The layout of the
keyboard is like that of traditional typewriter, although there are some additional keys provided for performing some additional
functions.Keyboard is of two sizes 84 keys or 101/102 keys, but now 104 keys or 108 keys keyboard is also available for Windows and
Internet.
2.Mouse
Mouse is most popular Pointing device. It is a very famous cursor-control device. It is a small palm size box with a round ball at its base
which senses the movement of mouse and sends corresponding signals to CPU on pressing the buttons.Generally it has two buttons
called left and right button and scroll bar is present at the mid. Mouse can be used to control the position of cursor on screen, but it
cannot be used to enter text into the computer.

Advantages
● Easy to use
● Not very expensive
● Moves the cursor faster than the arrow keys of keyboard.
3.Scanner
Scanner is an input device which works more like a photocopy machine. It is used when some information is available on a paper
and it is to be transferred to the hard disc of the computer for further manipulation.
Scanner captures images from the source which are then converted into the digital form that can be stored on the disc. These
images can be edited before they are printed.
4.Joystick
A joystick is also a pointing device which is used to move the cursor position on a monitor screen. It is a stick having a spherical
ball at its both lower and upper ends. The lower spherical ball moves in a socket. The Joystick can be moved in all four directions.
The function of a joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing
computer games.

5.Light Pen
A light pen is a pointing device which is similar to a pen. It is used to select a displayed menu item or draw pictures on the
monitor screen. It consists of a photocell and an optical system placed in a small tube. When the light pen’s tip is moved over
the monitor screen and the pen button is pressed, its photocell sensing element detects the screen location and sends the
corresponding signal to the CPU.
6.Magnetic Ink Card Reader (MICR)
The MICR input device is generally used in banks because of a large number of cheques to be processed every day. The bank’s
code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic
material that are machine readable.This reading process is called Magnetic Ink Character Recognition (MICR). The main
advantage of MICR is that it is fast and less error prone.
7.Optical Character Reader(OCR)
OCR is an input device used to read a printed text. OCR scans text optically character by character, converts them into a
machine readable code and stores the text on the system memory.

8.Bar Code Readers
Bar Code Reader is a device used for reading bar coded data (data in form of light and dark lines). Bar coded data is generally used
in labelling goods, numbering the books etc. It may be a handheld scanner or may be embedded in a stationary scanner.
Barcode Reader scans a barcode image, converts it into an alphanumeric value which is then fed to the computer to which the bar
code reader is connected.
9.Optical Mark Reader (OMR)
OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few
alternatives is to be selected and marked. It is specially used for checking the answer sheets of examinations having multiple choice
questions.
10.Touch screen
The touch screen is an input device. Touch screen technology is the direct manipulation type gesture based technology. Direct
manipulation is the ability to manipulate the digital world inside a screen without the use of command-line-commands. A device
which works on touch screen technology is coined as Touch screen. A touch screen is an electronic visual display capable of
‘detecting’ and effectively ‘locating’ a touch over its display area.
It is sensitive to the touch of a human finger, hand, pointed finger nail and passive objects like stylus. Users can simply move things
on the screen, scroll them, make them bigger and many more.

Output Devices
A device which is used to display results from a computer is called an output device.
It allows people to receive information from computers. An output device is any peripheral that receives or displays output from a
computer. The picture shows an inkjet printer, an output device that can make a hard copy of anything being displayed on a
monitor. An output device is electronic equipment connected to a computer and used to transfer data out of the computer in the
form of text, images, sounds or print.
Examples of output devices include : Digitizers, Plotters, LCD, Plasma Display, Printers, etc.
Digitizer
Digitizer is an input device which converts analog information into a digital form. Digitizer can convert a signal from the
television camera into a series of numbers that could be stored in a computer. They can be used by the computer to create a picture
of whatever the camera has been pointed at.
Digitizer is also known as Tablet or Graphics Tablet because it converts graphics and pictorial data into binary inputs. A graphic
tablet as a digitizer is used for doing fine works of drawing and images manipulation applications.

Plotters
A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated
pens. Unlike a regular printer, the plotter can draw continuous point-to-point lines directly from vector graphics files or
commands. There are a number of different types of plotters: a drum plotter draws on paper wrapped around a drum which turns
to produce one direction of the plot, while the pens move to provide the other direction; a flatbed plotter draws on paper placed
on a flat surface; and an electrostatic plotter draws on negatively charged paper with positively charged toner.Plotters were the
first type of printer that could print with color and render graphics and full-size engineering drawings. As a rule, plotters are
much more expensive than printers. They are most frequently used for CAE (computer-aided engineering) applications, such as
CAD (computer-aided design) and CAM (computer-aided manufacturing).
Monitors
A monitor commonly called a Visual Display Unit (VDU) is the main output device of a computer. It forms images from tiny
dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the no. of the pixels.
There are three kinds of viewing screens used for monitors.
● Cathode-Ray Tube (CRT)
● Liquid Crystal Display (LCD)
● Plasma Display
Printers
Printer is the most important output device, which is used to print information on paper.
There are two types of printers
● Impact Printers
● Non-Impact Printers

Impact Printers
The printers that print the characters by striking against the ribbon and onto the paper are called impact printers.
Characteristics of Impact Printers are following
● Very low consumable costs
● Impact printers are very noisy
● Useful for bulk printing due to low cost
● There is physical contact with the paper to produce an image
These printers are of two types
● Character printers
● Line printers
Character Printers:
Character Printers are printers which print one character at a time.
These are of further two types
● Dot Matrix Printer(DMP)
● Daisy Wheel
Dot Matrix Printer
In the market one of the most popular printers is Dot Matrix Printer because of their ease of printing features and economical price.

Advantages
● Inexpensive
● Widely Used
● Other language characters can be printed
Disadvantages
● Slow Speed
● Poor Quality
Line Printers
Line printers are printers which print one line at a time.
These are of further two types
● Drum Printer
● Chain Printer
Drum Printer
This printer is like a drum in shape so it is called drum printer.
Advantages
● Very high speed
Disadvantages
● Very expensive
● Characters fonts can not be changed

Chain Printer
In this printer chain of character sets are used so it is called Chain Printers.
Advantages
● Character fonts can easily be changed.
● Different languages can be used with the same printer.
Disadvantages
● Noisy
● Do not have the ability to print any shape of characters.
Non-impact Printers
The printers that print the characters without striking against the ribbon and onto the paper, are called Non-impact Printers. These
printers print a complete page at a time, also called Page Printers.
These printers are of two types
● Laser Printers
● Inkjet Printers
Characteristics of Non-impact Printers
● Faster than impact printers.
● High quality.
● Support many fonts and different character sizes.

Laser Printers
These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.
Advantages
● Very high speed.
● Very high quality output.
● Give good graphics quality.
● Support many fonts and different character sizes.
Disadvantage
● Cannot be used to produce multiple copies of a document in a single printing.
Inkjet Printers
Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of
ink onto paper. Inkjet printers produce high quality output with presentable features.

PRIMARY MEMORY AND SECONDARY STORAGE
PRIMARY MEMORY
Primary memory is a segment of computer memory that can be accessed directly by the processor. In a hierarchy of memory, primary
memory have access time less than secondary memory and greater than cache memory. Generally, primary memory has a storage
capacity lesser than secondary memory and greater than cache memory.
Need of primary memory
In order to enhance the efficiency of the system, memory is organized in such a way that access time for the ready process is minimized.
The following approach is followed to minimize access time for the ready process.
● All programs, files, and data are stored in secondary storage that is larger and hence has greater access time.
● Secondary memory can not be accessed directly by a CPU or processor.
● In order to execute any process, the operating system loads the process in primary memory which is smaller and can be
accessed directly by the CPU.
● Since only those processes are loaded in primary memory which is ready to be executed, the CPU can access those processes
efficiently and this optimizes the performance of the system.

This organization of memory in a stepwise manner is known as Memory Hierarchy.
Classification of Primary Memory
Primary memory can be broadly classified into two parts:
1. Read-Only Memory (ROM)
2. Random Access Memory (RAM)

Read-Only Memory
Any data which need not be altered are stored in ROM. ROM includes those programs which run on booting of the system (know
as a bootstrap program that initializes OS) along with data like algorithm required by OS. Anything stored in ROM cannot be altered
or changed.
Types of ROM:
ROM can be broadly classified into 4 types based on their behavior:
● MROM: Masked ROM are hardwired and pre-programmed ROM. Any content that is once written cannot be altered
anyhow.
● PROM: Programmable ROM can be modified once by the user. The user buys a blank PROM and writes the desired
content but once written content cannot be altered.
● EPROM: Erasable and Programmable ROM Content can be changed by erasing the initial content which can be done by
exposing EPROM to UV radiation. This exposure to ultra-violet light dissipates the charge on ROM and content can be
rewritten on it.
● EEPROM: Electrically Erasable and Programmable ROM Content can be changed by erasing the initial content which
could be easily erased electrically. However, one byte can be erased at a time instead of being deleted in one go. Hence,
reprogramming of EEPROM is a slow process.

Random Access Memory
Any process in the system which needs to be executed is loaded in RAM which is processed by the CPU as per Instructions in the program.
Like if we click on applications like Browser, firstly browser code will be loaded by the Operating system into the RAM after which the
CPU will execute and open up the Browser.
Types of RAM:
RAM can be broadly classified into SRAM (Static RAM) and DRAM (Dynamic RAM) based on their behavior:
● DRAM: Dynamic RAM or DRAM needs to periodically refresh in few milliseconds to retain data. DRAM is made up of
capacitors and transistors and electric charge leaks from capacitors and DRAM needs to be charged periodically. DRAM is
widely used in home PCs and servers as it is cheaper than SRAM.
● SRAM: Static RAM or SRAM keeps the data as long as power is supplied to the system. SRAM uses Sequential circuits like a
flip-flop to store a bit and hence need not be periodically refreshed. SRAM is expensive and hence only used where speed is the
utmost priority.
SECONDARY STORAGE/MEMORY
In a computer, memory refers to the physical devices that are used to store programs or data on a temporary or permanent basis. It is a group
of registers. Memory are of two types (i) primary memory, (ii) secondary memory. Primary memory is made up of semiconductors, It is also
divided into two types, Read-Only Memory (ROM) and Random Access Memory (RAM). Secondary memory is a physical device for the
permanent storage of programs and data(Hard disk, Compact disc, Flash drive, etc.).

Primary memory is volatile and has limited capacity. So, it is important to have another form of memory that has a larger
storage capacity and from which data and programs are not lost when the computer is turned off. Such a type of memory is
called secondary memory. In secondary memory, programs and data are stored. It is also called auxiliary memory. It is
different from primary memory as it is not directly accessible through the CPU and is non-volatile. Secondary or external
storage devices have a much larger storage capacity and the cost of secondary memory is less as compared to primary
memory.

Use of Secondary memory
Secondary memory is used for different purposes but the main purposes of using secondary memory are:
● Permanent storage: As we know that primary memory stores data only when the power supply is on, it loses data when the
power is off. So we need a secondary memory to stores data permanently even if the power supply is off.
● Large Storage: Secondary memory provides large storage space so that we can store large data like videos, images, audios,
files, etc permanently.
● Portable: Some secondary devices are removable. So, we can easily store or transfer data from one computer or device to
another.
Types of Secondary memory
Secondary memory is of two types:
1. Fixed storage
In secondary memory, a fixed storage is an internal media device that is used to store data in a computer system. Fixed storage is
generally known as fixed disk drives or hard drives. Generally, the data of the computer system is stored in a built-in fixed storage device.
Fixed storage does not mean that you can not remove them from the computer system, you can remove the fixed storage device for
repairing, for the upgrade, or for maintenance, etc. with the help of an expert or engineer.

Types of fixed storage:
Following are the types of fixed storage:
● Internal flash memory (rare)
● SSD (solid-state disk)
● Hard disk drives (HDD)
2. Removable storage
In secondary memory, removable storage is an external media device that is used to store data in a computer system. Removable storage is
generally known as disks drives or external drives. It is a storage device that can be inserted or removed from the computer according to
our requirements. We can easily remove them from the computer system while the computer system is running. Removable storage
devices are portable so we can easily transfer data from one computer to another. Also, removable storage devices provide the fast data
transfer rates associated with storage area networks (SANs).
Types of Removable Storage:
● Optical discs (like CDs, DVDs, Blu-ray discs, etc.)
● Memory cards
● Floppy disks
● Magnetic tapes
● Disk packs
● Paper storage (like punched tapes, punched cards, etc.)

Secondary memory devices
Following are the commonly used secondary memory devices are:
1. Floppy Disk: A floppy disk consists of a magnetic disc in a square plastic case. It is used to store data and to transfer data from one device
to another device. Floppy disks are available in two sizes (a) Size: 3.5 inches, the Storage capacity of 1.44 MB (b) Size: 5.25 inches, the
Storage capacity of 1.2 MB. To use a floppy disk, our computer needs to have a floppy disk drive. This storage device becomes obsolete now
and has been replaced by CDs, DVDs, and flash drives.
2. Compact Disc: A Compact Disc (CD) is a commonly used secondary storage device. It contains tracks and sectors on its surface. Its shape
is circular and is made up of polycarbonate plastic. The storage capacity of CD is up to 700 MB of data. A CD may also be called a CD-ROM
(Compact Disc Read-Only Memory), in this computers can read the data present in a CD-ROM, but cannot write new data onto it. For a CD-
ROM, we require a CD-ROM. CD is of two types:
● CD-R (compact disc recordable): Once the data has been written onto it cannot be erased, it can only be read.
● CD-RW (compact disc rewritable): It is a special type of CD in which data can be erased and rewritten as many times as we
want. It is also called an erasable CD.
3. Digital Versatile Disc: A Digital Versatile Disc also known as DVD it is looks just like a CD, but the storage capacity is greater compared
to CD, it stores up to 4.7 GB of data. DVD-ROM drive is needed to use DVD on a computer. The video files, like movies or video
recordings, etc., are generally stored on DVD and you can run DVD using the DVD player. DVD is of three types:
● DVD-ROM(Digital Versatile Disc Readonly): In DVD-ROM the manufacturer writes the data in it and the user can only read
that data, cannot write new data in it. For example movie DVD, movie DVD is already written by the manufacturer we can only
watch the movie but we cannot write new data into it.
● DVD-R(Digital Versatile Disc Recordable): In DVD-R you can write the data but only one time. Once the data has been written
onto it cannot be erased, it can only be read.
● DVD-RW(Digital Versatile Disc Rewritable and Erasable): It is a special type of DVD in which data can be erased and
rewritten as many times as we want. It is also called an erasable DVD.

4. Blu-ray Disc: A Blu-ray disc looks just like a CD or a DVD but it can store data or information up to 25 GB data. If you want to
use a Blu-ray disc, you need a Blu-ray reader. The name Blu-ray is derived from the technology that is used to read the disc ‘Blu’
from the blue-violet laser and ‘ray’ from an optical ray.
5. Hard Disk: A hard disk is a part of a unit called a hard disk drive. It is used to storing a large amount of data. Hard disks or hard
disk drives come in different storage capacities.(like 256GB, 500 GB, 1 TB, and 2 TB, etc.). It is created using the collection of discs
known as platters. The platters are placed one below the other. They are coated with magnetic material. Each platter consists of a
number of invisible circles and each circle having the same centre called tracks. Hard disk is of two types (i) Internal hard disk (ii)
External hard disk.
6. Flash Drive: A flash drive or pen drive comes in various storage capacities, such as 1 GB, 2 GB, 4 GB, 8 GB, 16 GB, 32 GB, 64
GB, up to 1TB. A flash drive is used to transfer and store data. To use a flash drive, we need to plug it into a USB port on a computer.
As a flash drive is easy to use and compact in size, Nowadays it is very popular.
7. Solid-state disk: It is also known as SSD. It is a non-volatile storage device that is used to store and access data. It is faster, does
noiseless operations(because it does not contain any moving parts like the hard disk), consumes less power, etc. It is a great
replacement for standard hard drives in computers and laptops if the price is low and it is also suitable for tablets, notebooks, etc
because they do not require large storage.
8. SD Card: It is known as a Secure Digital Card. It is generally used in portable devices like mobile phones, cameras, etc., to store
data. It is available in different sizes like 1 GB, 2 GB, 4 GB, 8 GB, 16 GB, 32 GB, 64 GB, etc. To view the data stored in the SD card
you can remove them from the device and insert them into a computer with help of a card reader. The data stores in the SD card is
stored in memory chips(present in the SD Card) and it does not contain any moving parts like the hard disk.

Difference between Primary and Secondary Memory
1. Basics of Primary and Secondary Memory
Memory plays a critical part in computers to store and retrieve data. Computer memory is categorized into primary and secondary
memory. While primary memory is the main memory of the computer which is used to store data or information temporarily, whereas
secondary memory refers to external storage devices that are used to store data or information permanently.
2. Access of Primary and Secondary Memory
Primary memory holds only those data or instructions which the computer is currently processing allowing the processor to access
running applications and services that are stored temporarily in a specific memory address. Secondary memory, on the other hand, is
persistent in nature which means instructions are transferred to the main memory first and then re-routed to the central processing unit.
3. Data in Primary and Secondary Memory
In primary memory, data is directly accessed by the processing unit and it resides in the main memory until processing. Information and
data are stored in semiconductor chips so they have a limited storage capacity. In secondary memory, information is stored in external
storage devices and they cannot be directly accessed by the processing unit.

4. Nature of Primary and Secondary Memory
Primary memory is volatile in nature which means data or information stored in the main memory is temporary which may lead to loss
of data in case of power failure and it cannot be retained. On the contrary, secondary memory is non-volatile in nature which means
information is stored permanently with no data loss in case of power failure. Data is intact unless the user erases it intentionally.
5. Devices for of Primary and Secondary Memory
Primary memory can also be referred to as RAM, short for Random Access Memory, because of the random selection of memory
addresses. RAM holds data in a uniform manner and it can be lost when power fails. Secondary memory refers to external storage
devices such as hard disk, optical disk, compact disk, flash drives, magnetic tapes, etc. They are high-storage devices with substantial
storage capacities, in the range of gigabytes to terabytes.
6. Speed of Primary and Secondary Memory
In primary memory, applications and instructions are stored in the main memory which makes them relatively faster to access via data
bus. Processor is able to retrieve data faster than it does with secondary memory, which acts more like a backup memory to store data in
external storage devices.

COMPUTER SOFTWARE
The hardware devices need user instructions to function. A set of instructions that achieve a single outcome are called program or
procedure. Many programs functioning together to do a task make a software.
For example, a word-processing software enables the user to create, edit and save documents. A web browser enables the user to view and
share web pages and multimedia files. There are three categories of software −
● System Software
● Application Software

System Software
Software required to run the hardware parts of the computer and other application software are called system software. System software
acts as interface between hardware and user applications. An interface is needed because hardware devices or machines and humans
speak in different languages.
Machines understand only binary language i.e. 0 (absence of electric signal) and 1 (presence of electric signal) while humans speak in
English, French, German, Tamil, Hindi and many other languages. English is the predominant language of interacting with computers.
Software is required to convert all human instructions into machine understandable instructions. And this is exactly what system software
does.
Based on its function, system software is of following types −
● Operating System
● Language Processor
● Device Drivers
Operating System
System software that is responsible for functioning of all hardware parts and their interoperability to carry out tasks successfully is
called operating system (OS). OS is the first software to be loaded into computer memory when the computer is switched on and this is
called booting. OS manages a computer’s basic functions like storing data in memory, retrieving files from storage devices, scheduling
tasks based on priority, etc.

Language Processor
An important function of system software is to convert all user instructions into machine understandable language. When we talk of
human machine interactions, languages are of three types −
● Machine-level language − This language is nothing but a string of 0s and 1s that the machines can understand. It is
completely machine dependent.
● Assembly-level language − This language introduces a layer of abstraction by defining mnemonics. Mnemonics are
English like words or symbols used to denote a long string of 0s and 1s. For example, the word “READ” can be
defined to mean that computer has to retrieve data from the memory. The complete instruction will also tell the
memory address. Assembly level language is machine dependent.
● High level language − This language uses English like statements and is completely independent of machines.
Programs written using high level languages are easy to create, read and understand.
Program written in high level programming languages like Java, C++, etc. is called source code. Set of instructions in machine
readable form is called object code or machine code. System software that converts source code to object code is called language
processor. There are three types of language interpreters−
● Assembler − Converts assembly level program into machine level program.
● Interpreter − Converts high level programs into machine level program line by line.
● Compiler − Converts high level programs into machine level programs at one go rather than line by line.

Device Drivers
System software that controls and monitors functioning of a specific device on computer is called device driver. Each device like printer,
scanner, microphone, speaker, etc. that needs to be attached externally to the system has a specific driver associated with it. When you attach
a new device, you need to install its driver so that the OS knows how it needs to be managed.
Application Software
A software that performs a single task and nothing else is called application software. Application software are very specialized in their
function and approach to solving a problem. So a spreadsheet software can only do operations with numbers and nothing else. A hospital
management software will manage hospital activities and nothing else. Here are some commonly used application software −
● Word processing
● Spreadsheet
● Presentation
● Database management
● Multimedia tools
Utility Software
Application software that assist system software in doing their work is called utility software. Thus utility software is actually a cross
between system software and application software. Examples of utility software include −
● Antivirus software
● Disk management tools
● File management tools
● Compression tools
● Backup tools

MALICIOUS SOFTWARE/MALWARE
Malware is a software that gets into the system without user consent with an intention to steal private and confidential data of the user that
includes bank details and password. They also generates annoying pop up ads and makes changes in system settings
They get into the system through various means:
1. Along with free downloads.
2. Clicking on suspicious link.
3. Opening mails from malicious source.
4. Visiting malicious websites.
5. Not installing an updated version of antivirus in the system.
Types:
6. Virus
7. Worm
8. Logic Bomb
9. Trojan/Backdoor
10. Rootkit
11. Advanced Persistent Threat
12. Spyware and Adware

Computer virus:
Computer virus refers to a program which damages computer systems and/or destroys or erases data files. A computer virus is a malicious
program that self-replicates by copying itself to another program. In other words, the computer virus spreads by itself into other executable
code or documents. The purpose of creating a computer virus is to infect vulnerable systems, gain admin control and steal user sensitive
data. Hackers design computer viruses with malicious intent and prey on online users by tricking them.
Symptoms:
● Letter looks like they are falling to the bottom of the screen.
● The computer system becomes slow.
● The size of available free memory reduces.
● The hard disk runs out of space.
● The computer does not boot
Worm:
A worm is a destructive program that fills a computer system with self-replicating information, clogging the system so that its operations
are slowed down or stopped.
Types of Worm:
1. Email worm – Attaching to fake email messages.
2. Instant messaging worm – Via instant messaging applications using loopholes in network.
3. Internet worm – Scans systems using OS services.
4. Internet Relay Chat (IRC) worm – Transfers infected files to web sites.
5. Payloads – Delete or encrypt file, install backdoor, creating zombie etc.
6. Worms with good intent – Downloads application patches.

Logical Bomb:
A logical bomb is a destructive program that performs an activity when a certain action has occurred. These are hidden in programming
code. Executes only when a specific condition is met, e.g. Jerusalem.
Script Virus:
Commonly found script viruses are written using the Visual Basic Scripting Edition (VBS) and the JavaScript programming language.
Trojan / Backdoor:
Trojan Horse is a destructive program. It usually pretends as computer games or application software. If executed, the computer system
will be damaged. Trojan Horse usually comes with monitoring tools and key loggers. These are active only when specific events are alive.
These are hidden with packers, crypters and wrappers. Hence, difficult to detect through antivirus. These can use manual removal or
firewall precaution.
RootKits:
Collection of tools that allow an attacker to take control of a system.
● Can be used to hide evidence of an attacker’s presence and give them backdoor access.
● Can contain log cleaners to remove traces of attacker.
● Can be divided as:
– Application or file rootkits: replaces binaries in Linux system
– Kernel: targets kernel of OS and is known as a loadable kernel module (LKM)
● Gains control of infected m/c by:
– DLL injection: by injecting malicious DLL (dynamic link library)
– Direct kernel object manipulation: modify kernel structures and directly target trusted part of OS
– Hooking: changing applicant’s execution flow

Advanced Persistent Threat:
Created by well funded, organized groups, nation-state actors, etc. Desire to compromise government and commercial entities, e.g. Flame:
used for reconnaissance and information gathering of systems.
Spyware and Adware:
Normally gets installed along with free software downloads. Spies on the end-user, attempts to redirect the user to specific sites. Main
tasks: Behavioral surveillance and advertising with pop up ads Slows down the system.
OPERATING SYSTEMS
An Operating System (OS) is a software that acts as an interface between computer hardware components and the user. Every computer
system must have at least one operating system to run other programs. Applications like Browsers, MS Office, Notepad Games, etc., need
some environment to run and perform its tasks.
The OS helps you to communicate with the computer without knowing how to speak the computer’s language. It is not possible for the
user to use any computer or mobile device without having an operating system.

Introduction to Operating System
Types of Operating System (OS)
Following are the popular types of OS (Operating System):
● Batch Operating System
● Multitasking/Time Sharing OS
● Multiprocessing OS
● Real Time OS
● Distributed OS
● Network OS
● Mobile OS
Batch Operating System
Some computer processes are very lengthy and time-consuming. To speed the same process, a job with a similar type of needs are batched
together and run as a group.
The user of a batch operating system never directly interacts with the computer. In this type of OS, every user prepares his or her job on an
offline device like a punch card and submit it to the computer operator.
Multi-Tasking/Time-sharing Operating systems
Time-sharing operating system enables people located at a different terminal(shell) to use a single computer system at the same time. The
processor time (CPU) which is shared among multiple users is termed as time sharing.

Real time OS
A real time operating system time interval to process and respond to inputs is very small. Examples: Military Software Systems, Space
Software Systems are the Real time OS example.
Distributed Operating System
Distributed systems use many processors located in different machines to provide very fast computation to its users.
Network Operating System
Network Operating System runs on a server. It provides the capability to serve to manage data, user, groups, security, application, and
other networking functions.
Mobile OS
Mobile operating systems are those OS which is especially that are designed to power smartphones, tablets, and wearables devices.
Some most famous mobile operating systems are Android and iOS, but others include BlackBerry, Web, and watchOS.
Functions of Operating System
Some typical operating system functions may include managing memory, files, processes, I/O system & devices, security, etc.

Below are the main functions of Operating System:
Functions of Operating System

In an operating system, software performs each of the function:
1.Process management: Process management helps the OS to create and delete processes. It also provides mechanisms for
synchronization
and communication among processes.
2.Memory management: Memory management module performs the task of allocation and deallocation of memory space to programs in
need of this
resources.
3.File management: It manages all the file-related activities such as organization storage, retrieval, naming, sharing, and protection of
files.
4.Device Management: Device management keeps track of all devices. This module also responsible for this task is known as the I/O
controller.
It also performs the task of allocation and deallocation of the devices.
5.I/O System Management: One of the main objects of any OS is to hide the peculiarities of hardware devices from the user.
6.Secondary-Storage: Management: Systems have several levels of storage which includes primary storage, secondary storage, and cache
storage.
Instructions and data must be stored in primary storage or cache so that a running program can reference it.
7.Security: Security module protects the data and information of a computer system against malware threat and authorized access.
8.Command interpretation: This module is interpreting commands given by the and acting system resources to process those commands.
9.Networking: A distributed system is a group of processors which do not share memory, hardware devices, or a clock.
The processors communicate with one another through the network.
10.Job accounting: Keeping track of time & resources used by various job and users.
11.Communication management: Coordination and assignment of compilers, interpreters, and other software resources of the various
users of the computer systems.

BASICS IN COMPUTER APPLICATIONS - UNIT I

More Related Content

What's hot

Similar to BASICS IN COMPUTER APPLICATIONS - UNIT I

Recently uploaded

BASICS IN COMPUTER APPLICATIONS - UNIT I