COMPUTER SYSTEM & ORGANISATION

UNIT:1  COMPUTER SYSTEM & ORGANISATION

Syllabus

Unit I: Computer Systems and Organisation

 

●       Basic Computer Organisation: Introduction to computer system, hardware, software, input device, output device, CPU, memory (primary, cache and secondary), units of memory (Bit, Byte, KB, MB,GB, TB, PB)

●       Types of software: system software (operating systems, system utilities, device drivers), programming tools and language translators (assembler, compiler & interpreter), application software

●       Operating system (OS): functions of operating system, OS user interface

●       Boolean logic: NOT, AND, OR, NAND, NOR, XOR, truth table, De Morgan’s laws and logic circuits

●       Number system: Binary, Octal, Decimal and Hexadecimal number system; conversion between number systems.

●       Encoding schemes: ASCII, ISCII and UNICODE (UTF8, UTF32)

 

Introduction  

Computers are seen everywhere around us, in all spheres of life. May it be the field of education and research, travel and tourism, weather forecasting, social networking, ecommerce or any other, computers have now become an indispensable part of our lives. The manner, in which computers have revolutionised our lives because of their accuracy and speed of performing a job, is truly remarkable. Today no organization can function without a computer. In fact various organizations are trying to become paper free owing to benefits of computers. But the computers of today have evolved over the years from a simple calculating device to the portable high speed computers that we see today.

Evolution of Computers

The growth of computer industry started with the need for performing fast calculations. The manual method of computing was slow and prone to errors. So attempts were made to develop faster calculating devices. The journey that started from the first calculating device i.e. Abacus has led us today to extremely high speed calculating devices. Let us first have a look at some early calculating devices and then we will explore various generations of computer.

Abacus

Abacus was discovered by the Mesopotamians in around 3000 BC. An abacus consisted of beads on movable rods divided into two parts. (Fig-1) Addition and multiplication of numbers was done by using the place value of digits of the numbers and position of beads in an abacus.

Napier’s Logs and Bones

The idea of logarithm was developed by John Napier in 1617. He devised a set of numbering rods known as Napier’s Bones through which both multiplication and division could be performed. These were numbered rods which could perform multiplication of any number by a number in the range of 2-9. There are 10 bones corresponding to the digits 0-9 and there is also a special eleventh bone that is used to represent the multiplier. By placing bones corresponding to the multiplier on the left 4 side and the bones corresponding to the digits of the multiplicand on the right , the product of two numbers can be easily obtained.

Pascaline

Blaise Pascal, a French mathematician invented an adding machine in 1642 that was made up of gears and was used for adding numbers quickly. This machine was also called Pascaline and was capable of addition and subtraction along with carry-transfer capability. It worked on clock work mechanism principle. It consisted of various numbered toothed wheels having unique position values. The addition and subtraction operations was performed by controlled rotation of these wheels.

Leibnitz’s Calculator

In 1673 Gottfried Leibnitz, a German mathematician extended the capabilities of the adding machine invented by Pascal to perform multiplication and division as well. The multiplication was done through repeated addition of numbers using a stepped cylinder each with nine teeth of varying lengths.

Jacquard’s Loom

In order to make the cotton weaving process automatic, Joseph Jaquard devised punch cards and used them to control looms in 1801. The entire operation was under a program’s control. Through this historic invention, the concept of storing and retrieving information started.

Father of Modern Computers: Charles Babbage

Difference engine and Analytical Engine

Charles Babbage, an English mathematician developed a machine called Difference Engine in 1822 which could calculate various mathematical functions, do polynomial evaluation by finite difference and theoretically could also solve differential equations. 

Thereafter in 1833, he designed the first mechanical computer namely- Analytical Engine which later on proved to be the basis of modern computer. This machine could perform all the four arithmetic operations as well as comparison. It included the concept of central processor, memory storage and input-output devices. Even the stored information could be modified.

Although the analytical engine was never built that time but Babbage established the basic principles on which today’s modern computers work.

Both these great inventions earned him the title of ‘Father of Modern Computers’.

Mark 1

In 1944 Prof Howard Aiken in collaboration with IBM constructed an electromechanical computer named Mark 1 which could multiply two 10 digit numbers in 5 seconds. This machine was based on the concept of Babbage’s Analytical engine and was the first operational general purpose computer which could execute preprogrammed instructions automatically without any human intervention.

In 1945, Dr. John Von Neumann proposed the concept of a stored program computer. As per this concept the program and data could be stored in the same memory unit. The basic architecture of the Von Neumann computer is shown in the figure below:

According to Von Neumann architecture, the processor executes instructions stored in the memory of the computer. Since there is only one communication channel, the processor at a time can either fetch data or an instruction. That means at one point of time either the data or an instruction can be picked (fetched) from the storage unit for execution by the processor. Hence execution takes place in sequential manner. This limitation of Von Neumann Computer is known as Von Neumann bottleneck. 

EDVAC

(Electronic Discrete Variable Automatic Computer) was the first stored program

computer developed in 1952. After the invention of first electronic computer. 

ENIAC

(Electronic Numerical Integrator and Calculator) in 1946, the computer technology improved tremendously and at very fast pace.

Generation of Computers

Growth in the computer industry is determined by the development in technology. Each phase/generation of computer development is characterized by one or more hardware/software developments that distinctly improved the performance of the computers of that generation. Based on various stages of development, computers can be divided into different generations.

The First Generation (1942-1955)

The first generation computers used the concept of ‘stored program’ and were characterized by vacuum tubes. A vacuum tube is a delicate glass device that can control and amplify electronic signals. The first generation computers were made using thousands of vacuum tubes and were the fastest calculating devices of their time. These computers were very large in size, consumed lot of electricity and generated lot of heat. 

UNIVAC 1 was the first electronic computer of this generation and was used for

business applications.

Salient features of First generation computers:

• Used vacuum tubes to control and amplify electronic signals
• Huge computers that occupied lot of space
• High electricity consumption and high heat generation
• Were unreliable since they were prone to frequent hardware failures
• Commercial production was difficult
• They were very costly and required constant maintenance
• Continuous air conditioning was required
• Programming was done in machine language although assembly language also started at the end of this generation 
• Example : ENIAC , EDVAC , UNIVAC 1

The Second Generation (1955–1964)

The second generation computers were characterized by transistors. A transistor is a solid state semiconductor device that revolutionized the electronic industry. Transistors were smaller, highly reliable, consumed less electricity and generated less heat. Also magnetic core memories were developed during this generation. These are tiny ferrite rings that can be magnetized in either clockwise or anticlockwise direction so as to represent binary 1 or binary 0. Magnetic cores were used as primary memories. Later magnetic disks also came into existence and were used as secondary storage devices.

All these new developments – transistors, magnetic core memory and magnetic disk storage devices made the computers more powerful and reliable. This further led to the existence of operating systems. Programming languages like FORTRAN, COBOL, Algol etc. also developed. Commercial applications of the computer increased and now the computers were used in business and industries for applications like payroll, employee management, inventory control etc. IBM 1401 and IBM 1620 were popular computers of this generation.

Salient Features of Second generation computers:

• Use transistor based technology
• Were smaller and less expensive as compared to first generation
• Consumed less electricity and emitted less heat
• Magnetic core memories and magnetic disks were used as primary and
• secondary storage respectively
• First operating system developed
• Programming in assembly language and in the later part high level languages were used
• Wider commercial use but commercial production was still difficult
• They also required constant air-conditioning.
• Examples: IBM 1401, IBM 1620, UNIVAC 1108

The Third Generation (1964-1975)

In 1964, the Integrated Circuits or ICs or chips revolutionized the electronic industry and started the third generation of computers. An IC is a small silicon chip or wafer made up of extremely purified silicon crystals. It has numerous transistors, capacitors, resistors and other elements of an electronic circuit. A small scale integration (SSI) chip used to have about 10 transistors on a single chip and a medium scale integration (MSI) chip had about 100 transistors per chip. The size of memories also increased. Various mainframe computers and minicomputers were developed during this generation. Even operating systems with multitasking and multiprogramming features were developed. Since ICs made the computers highly reliable, relatively inexpensive and faster, computers these days were found in areas of education, small businesses and offices along with industrial and business applications. IBM 360 was a very popular third generation computer.

Salient Features of Third Generation computers:

• Used integrated circuits
• Computers were smaller , faster and more reliable
• Low power consumption and less emission of heat as compared to previous generations
• Examples: IBM 360 series, Honeywell 6000 series

The Fourth Generation (1975 onwards)

In this generation Large Scale Integration (LSI) and Very Large scale integration (VLSI) technology was used by which up to 300,000 transistors were used on a single chip. Thus integration of complete CPU on a single chip was achieved in 1971 and was named microprocessor which marked the fourth generation of computers. The computers based on microprocessor technology had faster accessing and processing speeds. In addition to this the increased memory capacity further made the computers more powerful and also more efficient operating systems were developed for these computers. New concepts of microprogramming, application software, databases, virtual memory etc were developed and used.

The computers that we use today belong to this generation. These portable computers can be carried from one place to another owing to their compact size. They are much more accurate. Even memory sizes have become phenomenal. Commercial production of these computers is easier and they are the least expensive, compared to the earlier generation computers.

Also computer networks starting coming up during this generation. It is today one of the most popular means to interact and communicate with people.

Salient features of Fourth generation Computers

• ICs with LSI and VLSI technology
• Microprocessors developed
• Portable computers developed
• Networking and data communication became popular
• Different types of secondary memory with high storage capacity and fast access developed
• Very reliable ,powerful and small in size
• Negligible power consumption and heat generation
• Very less production cost

Fifth Generation Computers

Fifth Generation computers are still under development. This generation is based on the concept of artificial intelligence. In simple terms the computers of this generation are supposed to behave like humans. The principles of parallel processing (many processors are grouped together) and superconductivity are being used to develop devices that respond to human languages and will have the ability to apply previously gained knowledge to execute a task. They will let them make decisions of their own to execute a task. Some applications like voice recognition, visual recognition are a step in this very direction.

Salient features of fifth generation computers:

• Parallel Processing
• Superconductivity
• Artificial Intelligence

Evaluation of Computing Devices ( at a glance)

Concept of Booting

When the computer is switched on, a copy of boot program is brought from ROM into the main memory. This process is called booting. The CPU first runs a jump instruction that transfers to BIOS (Basic Input output System) and it starts executing. The BIOS conducts a series of self diagnostic tests called POST (Power On Self Test). These tests include memory tests, configuring and starting video circuitry, configuring the system’s hardware and checking other devices that help to function the computer properly.

Thereafter the BIOS locates a bootable drive to load the boot sector. The execution is then transferred to the Boot Strap Loader program on the boot sector which loads and executes the operating system. If the boot sector is on the hard drive then it will have a Master Boot record (MBR) which checks the partition table for active partition. If found, the MBR loads that partition’s boot sector and executes it.

Booting Process is of two types – Warm and Cold

Cold Booting: When the system starts from initial state i.e. it is switched on, we call it cold booting or Hard Booting. When the user presses the Power button, the instructions are read from the ROM to initiate the booting process.

Warm Booting: When the system restarts or when Reset button is pressed, we call it Warm Booting or Soft Booting. The system does not start from initial state and so all diagnostic tests need not be carried out in this case. There are chances of data loss and system damage as the data might not have been stored properly.

Classification of Computers

The computers can be classified based on the technology being used as: 
Digital, Analog and Hybrid

Digital Computers:

These computers are capable of processing information in discrete form. In digital technology data which can be in the form of letters, symbols or numbers is represented in binary form i.e. 0s and 1s. Binary digits are easily expressed in a digital computer by the presence (1) or absence (0) of current or voltage. It computes by counting and adding operations. The digital computers are used in industrial, business and scientific applications. They are quite suitable for large volume data processing.

Analog Computers:

An analog computer works on continuously changeable aspects of physical
phenomenon such as fluid pressure, mechanical motion and electrical quantities. These computers measure changes in continuous physical quantities say current and voltage.
These computers are used to process data generated by ongoing physical processes. A thermometer is an example of an analog computer since it measures the change in mercury level continuously. Although the accuracy of an analog computer is less as compared to digital computers, yet it is used to process data generated by changing physical quantities especially when the response to change is fast. Most present day analog computers are well suited to simulating systems. A simulator helps to conduct
experiments repeatedly in real time environment. Some of the common examples are simulations in aircrafts, nuclear power plants, hydraulic and electronic networks.

Hybrid Computers:

These use both analog and digital technology. It has the speed of analog computer and the accuracy of a digital computer. It may accept digital or analog signals but an extensive conversion of data from digital to analog and analog to digital has to be done.
Generally the analog components provide efficient processing of differential equations while the digital part deals with logical operations of the system. Hence benefits of both analog and digital computing are readily available. Hybrid Computers are used as a cost effective means for complex simulations.

Classification of Digital Computers

The digital computers are classified according to their computing capabilities. The various types of digital computers are discussed below:

Micro Computers

These are also known as Personal Computers. These type of digital computer uses a microprocessor (a CPU on a single chip) and include both desktops and laptops. These computers can work on small volume of data, are very versatile and can handle variety of applications. These computers are being used as work stations, CAD, multimedia and advertising applications. Small portable computers such as PDAs (Personal Digital Assistants) and tablets with wireless computing technology are increasingly becoming popular.

Mini Computers

These computers can support multiple users working simultaneously on the same machine. These are mainly used in an organization where computers installed in various departments are interconnected. These computers are useful for small business organizations.

Main Frames

These computers are large and very powerful computers with very high memory
capacity. These can process huge databases such as census at extremely fast rate. They are suitable for big organizations, banks, industries etc. and can support hundreds of users simultaneously on the network.

Super Computers

These are fastest and very expensive computers. They can execute billions of
instructions per second. These are multiprocessor, parallel systems suitable for
specialized complex scientific applications involving huge amounts of mathematical applications such as weather forecasting. The main difference between a supercomputer and a mainframe is that a supercomputer executes fewer programs as fast as possible whereas a mainframe executes many programs concurrently.

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Introduction to Computer System

Computer is an electronic device, which takes input from its user, process it according to the instructions given and produce a result called output. or we can say that a computer system is a set of integrated devices that input, output, process, and store data and information.

IPO cycle (Input Process Output): in this cycle instructions are given, processed and executed.

INPUT : This is the first step where instructions or data are given to the computer through keyboard or mouse. This unit is known as input unit.

PROCESS : This is the second step where processing is carried out i.e. execution of instructions. This unit is known as Central Processing Unit (CPU).

OUTPUT : This is the third step where result of a processing is displayed on the screen of the computer.

 

Now let us see the interconnection between these units:

HARDWARE AND SOFTWARE:

The computer is the combination of hardware and software.

Hardware are the physical components of the computer system. They are tangible in nature (i.e. one can touch the hardware components like motherboard, monitor, keyboard.)

 

Software are the logical components of the computer system. They are intangible in nature (i.e. one cannot touch software). Software is the set of programs or instructions. it helps in maintaining the computer system and performing the various tasks with the computer system

Both hardware and software together make the computer system function.

 

Input Devices: Devices that help user to give input to a computer are called Input Devices.

e.g.

• Keyboard: Basic Input Device for key entry

• Mouse : pointing device, input through four basic operation, Click, Double Click, Right Click, Drag.

• BCR (Bar Code Reader) : group of dark lines of varying thickness, generally used to obtain details of products in superstore

• OMR (Optical Mark Reader ): Input through dark spots on paper, generally used for conducting tests based on multiple choice pattern.

• OCR (Optical Character Reader ): mechanism to read printed text or convert printed text into editable form.

• MICR (Magnetic Ink Character Reader): used in processing of cheques in Bank

• Joystick : used in playing Games

• Mic or microphone : to provide sound input

• Scanner: to convert a hard copy (printed matter) to soft copy.

• Camera: to obtain photographs or video.

Output Devices : Devices, which display the result of processing are known as Output Devices. 

Examples

• Monitor : also known as VDU or visual display unit. This is the basic output unit of computer. 99% output is shown on Monitor only. There are various types of Monitors:-

       CRT or Cathode Ray Tube Monitor

       LED or Light Emitting Diode Monitor

       TFT or Thin Film Transistor

• Printers: Printers are used to obtain a hard of the output.

• Plotters : Plotters are heavy duty printers that are used to print Vector Graphics.

• Projector : Projectors are used to display the output on a screen.

• Speakers : to produce sound output.

MEMORY

CENTRAL PROCESSING UNIT (CPU)

CPU is called brain of the computer. It is also known as processor. It is responsible for carrying out all activities in a computer. It is further divided into three parts:

· Arithmetic Logic Unit (ALU): This unit is responsible for arithmetic calculations and comparison.

· Control Unit (CU): This unit is responsible for flow of data and instructions between different units of computer. It decides whether data should go to ALU, registers, memory unit, secondary storage or output unit.

· Registers: They are memory cells inside CPU to store data temporarily. They are mainly used to store frequently used data.

MEMORY UNIT

Memory unit is used to store data and instructions. It stores data in machine language

i.e. in the form of 0 and 1. The binary digits 0 and 1 are known as bits.

PRIMARY MEMORY: Memory unit is also termed as primary memory. It consists of three parts:

· RAM (Random Access Memory)

· ROM (Read Only Memory)

· Cache Memory

RAM (Random Access Memory): It is used to store data and instructions temporarily. It retains data in it as long as the power is on. All the contents of RAM get cleared if power supply is turned off.

Types of RAM:

· DYNAMIC RAM: It consists of capacitors and transistors. It uses electric charge to store the data.

· STATIC RAM: It consists of flip-flops. It stores data in binary form. It has faster access time compared to dynamic RAM.



ROM (Read Only Memory) : ROM stands for Read Only Memory. Data is permanently stored in ROM. it contains instructions needed to start up the computer and load operating system into RAM.
Types of ROM:

· PROM (Programmable Read Only Memory) : It can be programmed once.

· EPROM (Erasable Programmable Read Only Memory): It can be erased by keeping ROM chip using     Ultraviolet light. It can be reprogrammed..

· EEPROM (Electrically Erasable Read Only Memory): It can be erased by electrical signal. It can also     be reprogrammed.


CACHE MEMORY:

It is special memory used to compensate the speed difference between CPU (very fast) and RAM (very slow). It stores the copies of frequently used data from RAM. Hence it reduces the time required to access data from primary memory.


MEMORY UNITS (Measurement of Data):

1 Bit = 0 or 1

1 Nibble= 4 Bits

1 Byte= 8 Bits

1 KB (Kilo Byte)= 1024 Bytes (210)

1 MB (Megabyte) = 1024 KB (1024 X 1024 Bytes)

1 GB (Gigabyte) = 1024 MB

1 TB (Terabyte) = 1024 GB

1 PB (Petabyte) = 1024 TB

1 EB (Exabyte) = 1024 PB

1 ZB (Zettabyte) = 1024 EB

SECONDARY STORAGE UNIT:

Secondary storage unit is used to store data permanently. It consists of different types of storage devices. Most commonly used storage devices are:

 

1)     Hard Disk: It is the most commonly used storage device to store data on a computer. It consists of multiple magnetic plates and heads to read and write data. Magnetic plates are further divided into tracks and sectors to store data. Maximum capacity of hard disk is 15TB.

2)     Compact Disk (CD): it is an optical disk to store data. it have a storage capacity of 700 MB. There are three types of CDs:

Ø  CD-ROM (Compact Disk Read Only Memory): These are pre-recorded CDs provided by manufacturers. Example: CDs containing softwares, games, ebooks etc.

Ø  CD-R (Compact Disk Recordable): Data can be recorded on these CDs only once.

Ø  CD-RW (Compact Disk Rewritable): These types of CDs can be erased and recorded multiple times.

3)     Digital Versatile Disk (DVD): it is an optical disk to store data and have a storage capacity of upto 17 GB. There are three types of DVDs:

Ø  DVD-ROM (Digital Versatile Disk – Read Only Memory): These are prerecorded DVDs provided by manufacturers. Example: DVDs containing movies etc.

Ø  DVD-R (Digital Versatile Disk – Recordable): Data can be recorded on these DVDs only once.

Ø  DVD-RW (Digital Versatile Disk – Rewritable):These types of DVDs can be erased and recorded multiple times. 

4)     Blu Ray Disk: it is optical disk that can store HD (High Definition) videos and data. They can store up-to 128 GB of data.

 

5)     Pen Drive : It is also called Flash memory. It is a solid state memory that can store more than 128GB of data.

TYPES OF SOFTWARE:

Software is defined as a collection of programs which are used for different purposes.

 There are three types of software:

1)     System Software

2)     Application Software

3)     Utility Software

 Classification of Software:

Categories of Software:

System software is used to perform functions related to general operations of computer system. It has two types:

I.      Operating System: it is an interface between user and computer. It takes instructions from user and further instructs hardware components to work. The results produced by hardware components are sent back to the user.

Example: Windows 10 , Unix, Linux, Android etc.

I.         Language Translators: These softwares are used to convert the High Level Language instructions into Machine Language instructions.

Types of language translators:

Ø  Compiler: It converts High Level Language program into machine language in one go.

Ø  Interpreter: It converts High Level Language program into machine language line by line.

Ø  Assembler: It converts assembly language into machine language.

 

Application software: it is used to perform specific operation on computer. It has two types:

Ø  General Purpose software: These softwares can be used by more than one type of user. Example: MS Word is a general purpose software that can be used by students, teachers as well as clerks.

Ø  Special Purpose / Customized Software: These softwares can be used by only one type of user. Example: Banking Data Management software can be used only by bank employees.

 

Utility Software :

These softwares are used to take backup, remove outdated file, recover data and other tasks that assist in smooth operation of computer.

Examples : Anti-Virus , Disk Defragmentation, Disk Clean, Backup, etc.

 

Device Driver: A device driver is a particular form of software application that allows one hardware device to interact with another hardware device .A device driver may also be called a software driver. Example connecting a PC to a printer.

 

OPERATING SYSTEM (OS)

Operating system is an interface between computer hardware and user. It is responsible for the management of activities and the sharing of the computer resources. Operating system is divided into two parts:

Ø  Shell: It accepts instructions from user and instructs kernel to perform further operations

Ø  Kernel: It accepts instructions from shell and instructs hardware devices to perform operations.

 

FUNCTIONS OF OPERATING SYSTEM : 

Ø  Process Management:- The operating system takes care of the allotment of CPU time to different processes. it can create and delete processes. It also provides mechanism for communication among processes. This deals with management of the Central Processing Unit (CPU). This is known as scheduling.

Ø  Memory Management:- The CPU and the I/O devices interact with the memory. When a program needs to be executed it is loaded onto the main memory till the execution is complete. Thereafter that memory space is freed and is available for other programs. The common memory management techniques used by the operating system are Partitioning and Virtual Memory. Operating System allocates and de-allocates memory to different softwares.

Ø  File Management:- It manages storage, retrieval, naming, sharing, and protection of files. It also manages the files, folders and directory systems on a computer. The file manager of the operating system helps to create, edit, copy, allocate memory to the file.

Ø  Device Management: The Operating System communicates with hardware and the attached devices and maintains a balance between them and the CPU. This is all the more important because the CPU processing speed is much higher than that of I/O devices. It is responsible allocation and de-allocation of the hardware devices to different programs. In order to optimize the CPU time, the operating system employs two techniques - Buffering and Spooling.

Ø  I/O System Management: It takes care of allocation and de-allocation of Input/Output devices to different programs.

 

Types of Operating System:

 

Operating system can be classified into the following types:

 

Ø  Single User OS: It is used on a standalone single computer for performing a single task. Operating systems for Personal Computers (PC) are single-user OS. Single user OS are simple operating system designed to manage one task at a time. MS-DOS is an example of single user OS.

Ø  Multiuser OS is used in mini computers or mainframes that allow same data and applications to be accessed by multiple users at the same time. The users can also communicate with each other. Example: -Linux and UNIX OS

Ø  Multiprocessing OS have two or more processors for a single running process. Processing takes place in parallel and is also called parallel processing. Linux, Example: UNIX and Windows 7 OS.

Ø  Time sharing Operating System: It allows execution of more than one tasks or processes concurrently. For this, the processor time is divided amongst different tasks. This division of time is also called time sharing. Example : Windows 95

Ø  Real Time Operating System: It is a multitasking operating system designed for real time applications like robotics.

Ø  Distributed Operating System: On a network data is stored and processed on multiple locations. The Distributed Operating System is used on networks as it allows shared data/files to be accessed from any machine on the network in a transparent manner.

Ø  Interactive Operating System: This is the operating system that provides a Graphic User Interface (GUI) through which the user can easily navigate and interact.

 

Commonly Used Operating Systems:

·         Windows: It is a GUI (Graphic User Interface) and various versions of Windows have been launched like Windows 95, Windows 98, Win NT, Windows XP, Windows 7 , 8 and Windows 10.

·         Linux:   Linux is a free and open software which means it is freely available for use and since its source code is also available so anybody can use it, modify it and redistribute it.

·         BOSS (Bharat Operating System Solutions): This is an Indian distribution of GNU/Linux. It consists of Linux operating system kernel, office application suite, Bharateeya Open Office, Internet browser (Firefox), multimedia applications and file sharing.

·         UNIX: It is a multitasking, multiuser operating system and is widely being used in a networked environment. It is a free Unix based operating system introduced by Sun Microsystems in 1992. It is now also known as Oracle Solaris.

·         SOLARIS is registered as compliant with Single UNIX Specification. It is quite scalable and is used on virtual machines.

OPERATING SYSTEM USER INTERFACE:

S.No.	User Interface	Purpose
1	Natural  Language  Interface (Voice based)	These types of user interfaces use languages like English, French, etc in a very humanistic way so that users don’t feel like they are talking to a robot. NLI can be verbal or written. In verbal interfaces, it feels like someone is talking to you and getting the work done for you. Examples: Apple’s SIRI,   Microsoft’s   Cortana,   Google’s Assistant and Amazon’s Alexa.
2	Menu-driven Interface (Touch based)	Menu-driven Interface is used for very specific purposes which only require a few options or a small menu to be given to the users. The options can be in the form of buttons which can be either touch-based or physical. It allows users to interact with the system simply using the touch input. Examples : ATM machines, Android and iOS.
3	Gesture-based Interface	Mobile phones based on Android and iOS as well as laptops allow users interact with the devices using gestures like waving, tilting, eye motion and shaking. This technology is evolving faster and it has promising potential for application in gaming, medicine and other areas.
4	Graphical User Interface	GUI allows users run programs or give instructions to the computer in the form of icons, menus and other visual options. The input devices used to interact with the GUI commonly include the mouse and the keyboard. Examples: Microsoft Windows, Ubuntu, Fedora and Macintosh.
5	Command-Line interface	CLI requires a user to enter the commands to perform different tasks like creating, opening, editing or deleting a file, etc. The primary input device used by the user for command based interface is the keyboard. Examples: MS-DOS and Unix.

Mobile Operating Systems (Mobile OS)

It is the operating system that operates on digital mobile devices like smart phones and tablets. It extends the features of a normal operating system for personal computers so as to include touch screen, Bluetooth, WiFi, GPS mobile navigation, camera, music player and many more. The most commonly used mobile operating systems are –

Android and Symbian

• Android: It is a Linux derived Mobile OS released on 5th November 2007 and by 2011 it had more than 50% of the global Smartphone market share. 
• It is Google’s open and free software that includes an operating system, middle-ware and some key applications for use on mobile devices. 
• Android applications are quiet user friendly and even one can easily customize the Smartphone with Android OS. 
• Various versions of Android OS have been released like 1.0, 1.5, 1.6, 2. x, 3.0 etc. Most Android phones use the 2.x release while Android 3.0 is available only for tablets. 
• The Android releases have dessert inspired code-names like Cupcake, Honeycomb, Ice Cream sandwich and Jelly Bean.
• Android 10 is the tenth major release and the 17th version of the Android mobile operating system. It was released on September 3, 2019.

Symbian

• Symbian: This Mobile OS by Nokia (currently being maintained by Accenture) designed for smartphones. 
• It offers high level of functional integration between communication and personal information management. 
• It has an integrated mail box and it completely facilitates the usage of all Google applications in your smartphone easily. 
• Symbian applications are easy to shut down as compared to Android applications. 
• Various versions like S60 series, S80 series, S90 series, Symbian Anna etc have been released. 
• The latest Symbian releases (Symbian Belle/Nokia Belle Feature Pack 2 / 2 October 2012 ) can support 48 languages.

Open Source Concepts

Software are mainly categorized into the following categories based on their licenses:

1. Proprietary
2. Shareware
3. Freeware
4. Open source
5. Free Software

• Proprietary : We pay a supplier for a copy of the software which these days may be supplied on physical media (disks) or downloaded from the Internet. We get the permission to  use the software on one or sometimes more than one machines. Examples of this type of software include Microsoft Office and Microsoft Windows.

• Shareware: Shareware is basically a software for trial purpose that the user is allowed to try for free, for a specified period of time. It is usually downloaded from the Internet. When the trial period ends, the software must be purchased or uninstalled.

• Freeware: Freeware software is free of cost and is usually bundled up with some operating system or any other software. Examples of freeware include Microsoft Internet Explorer which comes bundled up with any Microsoft operating system. The author of the freeware software is the owner of the software, though people may use it for free. The source code is not available, so no modifications can be done. Freeware should not be mistaken with Open Source Software or Free Software.

• Open source : Open Source Software (OSS) is the software which gives the users freedom to run/use the software for  any purpose and in any manner. They can be used, modified and even redistributed. In simple terms it can be freely used but it may not be free of charge. The source code is freely available to the customer. LAMP ( Linux, Apache, MySQL, PHP) ,Python, MySQL etc are examples of Open Source Software.

• Free Software: This type of software is freely accessible and can be freely used, modified, copied or distributed by anyone. And no licence fee or any other form of payment need to be made for a free software. The source code is also accessible in case of free softwares. WordPress is an example of free software released under the GPL or General Public License.

Antivirus

An antivirus is utility software which detects and removes computer viruses. If the software is not able to remove the virus, it is neutralized. The antivirus keeps a watch on the functioning of the computer system. If a virus is found it may alert the user, flag the infected program or kill the virus. Some of the common types of viruses are:

• Boot Sector Virus: A boot sector virus displaces the boot record and copies itself to the boot sector i.e. where the program to boot the machine is stored. So first the virus is loaded on to the main memory and then the operating system. Whenever a new disk is inserted the virus copies itself to the new disk. The antivirus overwrites the correct boot record on the infected boot sector and also cleans the bad sectors.
• File Virus: A file virus generally attacks executable files. They can attach to various locations of the original file, replace code, fill in open spaces in the code, or create companion files to work with an executable file. Most of the file viruses are memory resident and wait in the memory until the user runs another program. While another program is running, the virus replicates.
• Macro Virus: This virus infects an important file called normal.dot of MS Word. As soon as the application is opened the virus gets activated. It damages the formatting of documents and even may not allow editing or saving of documents.
• Trojan Horse: It is a code generally hidden in games or spreadsheets. Since they are hidden, the program seems to function as the user wants but actually it is destroying the program. A Trojan horse does not require a host program to embed itself. It is a complete program. Its main objective is to cause harm to the data. They can create bad sectors on the disk, destroy file allocation tables and cause the system to hang. 
• Worm: Worm is a program capable of replicating itself on a computer network. A worm also does not require a host as it is a self contained program. They generally travel from one computer to another across communication links on a network. They generally disrupt routine services. 

Disk Defragmenter

The memory is used in small chunks randomly. Sometimes when a memory chunk of appropriate size is not available, the operating system breaks or fragments the files resulting in slower access to files. A disk defragmenter scans the hard disk for fragmented files and brings all the fragments together.

Backup Utility

This utility is used to create the copy of the complete or partial data stored in a disk or CD on any other disk. In case the hard disk crashes or some other system failure occurs, the files can be restored using backup software. 

Compression Utility

This utility is used to compress large files. Compression is useful because it helps reduce resources usage and the file transmission on the network becomes easier. 

Disk Cleaner

This utility scans for file that have not been accessed/used since long. Such files

might be occupying huge amount of memory space. In that case the Disk Cleaner

utility prompts the user to delete such files so as to create more space on the disk.

If the files are important, the user might take a backup before deleting them.

File Management Tools

This utility helps the user in storing, indexing, searching and sorting files and folders on the system. The most commonly used tool is the Windows Explorer and Google Desktop.

Encoding schemes: ASCII, ISCII and UNICODE (UTF8, UTF32):

 

Computers are designed to work internally with numbers. In order to handle characters, we need to choose a number for each character. The ability of a computer system to understand signals or letters depends on its character set

The complete set of characters / symbols are called alphanumeric codes. The complete

alphanumeric code typically includes −

Ø  26 upper case letters (A-Z)

Ø  26 lower case letters (a-z)

Ø  10 digits (0-9)

Ø  7 punctuation marks

Ø  20 to 40 special characters

Following are some forms of character set or encoding schemes:

Ø  ASCII

Ø  ISCII

Ø  UNICODE

ASCII Code: (American Standard Code for Information Interchange) most of the micro computers, mini computers and some mainframe computers use this code.

ASCII code has two versions - ASCII – 7 and ASCII – 8.

Ø  ASCII – 7 code use 7 bits for one signal or character. By this, 27 = 128 , different characters can be used.

Ø  ASCII – 8 code use 8 bits for one signal or character. By this, 28 = 256 , different characters can be used.

ISCII: it stands for Indian Script Code for Information Interchange for Indian languages. In order to facilitate the use of Indian languages on Computers, a common standard for coding Indian scripts called ISCII was developed in India.

It is an 8-bit code representation for Indian languages which means it can represent 28=256 characters. It retains all 128 ASCII codes and uses rest of the codes 128 for additional Indian language character set. Additional codes have been assigned in the upper region (160– 255) for the ‘aksharas’ of the language. These codes are used for ten Indian scripts - Devnagari, Punjabi, Gujarati, Oriya, Bengali, Assamese, Telugu, Kannada, Malayalam and Tamil.

UNICODE: (UNIVERSAL CODE)

This is Universal Character Set which represents a signal or a character in a group of 32 bit. It has the capability to include signals and characters from all scripts of all languages of world.

The Unicode Standard is the universal character encoding standard for written characters and text. Each character or symbol is assigned a unique numeric value, largely within the framework of ASCII. Earlier, each script had its own encoding system, which could conflict with each other.

The purpose of Unicode is to −

provide a unique number for every character, no matter what the platform,

no matter what the program, no matter what the language.

Unicode characters are represented in one of three encoding forms:

Ø  an 8-bit form (UTF-8)

Ø  a 16-bit form (UTF-16)

Ø  a 32-bit form (UTF32)

EXERCISES

1. The physical and tangible components of the computer are termed as:

     a) Hardware      b) software       c) firmware      d) None

2. The smallest memory unit is:

     a) bit      b) byte      c) kilobyte     d) megabyte

3. Antivirus is a type of which software:

a) System software   b) Application software   c) Utility Software   d) Firmware

4. A computer program that converts an entire program into machine language is called-

a) Interpreter     b) Compiler      c) Linker      d) Assembler

5. Which of the following is not a multi-user operating system?

a) DOS      b) Windows      c) Linux     d) Unix

6. Which of the following are two main components of CPU?

a) ALU & MU       b) ALU & CU      c) I/O     d) None

7. Which keyboard is used by visually impaired users?

a) Analog Keyboard      b) Digital Keyboard      c) Braille Keyboard     d) None

8. Which of the following is volatile memory?

a) RAM      b) ROM      c) Both a & b      d) None

9. Operating system with touch-based interface is……….

a) Andriod      b) ios      c) both a & b      d) None

10. Spreadsheet is an example of:

a) Application Software     b) System Software     c) firmware     d) liveware



SHORT ANSWER TYPE QUESTIONS :

Q. 1. Which part interprets program instructions and initiate control operations ? 

Ans. : Control unit.

Q. 2. What is the difference between data and information ?

Ans.: Data means facts and figures. Information means what we get after processing data i.e., processed data.

Q. 3. What is booting ? What are the types of booting ?

Ans.: Booting is the process of restarting a computer or its operating system software. It starts with switching on the computer and ends when the operating System is loaded in main memory and the computer is ready to take commands from the user.

Booting is of two types :

Cold booting : When the computer is started after having been switched off.

Warm booting : When the operating system alone is restarted after a system crash.

Q. 4. What is a bit ? How bit, byte and nibbles are related to each other?

Ans. : A bit is the smallest elementary unit of memory, which can store one binary signal either 0 or 1. A group of 8 bits is called a byte. A group of 4 bits is called a nibble.

Q. 5. What do you understand by IPO cycle?

Ans. : IPO cycle refers to the Input Process Output cycle where every operation undergoes the phases namely input, process and output.

LONG ANSWER TYPE QUESTIONS

Q. 1. Explain four characteristics of computer :

• 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.
• 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 30 decimal places.

• 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.

• 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 DVD and compact disk can store a large amount of data permanently.

Q. 2 Expand the following terms:

CPU, ALU, VLSI, MSI, LSI, SSI, IC, IPO, HLL, MB.

Ans. :

CPU —> Central Processing Unit 

ALU —> Arithmetic Logic Unit
VLSI —> Very Large-Scale Integration 

MSI —> Medium Scale Integration

LSI —> Large Scale Integration
SSI —> Small Scale Integration 

IC —> Integrated Circuits
IPO —> Input Process Output 

HLL —> High Level Language 

MB —> Mega Byte

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