COMPUTER REFRESHER FOR IBPS RRB - bsc4success · PDF fileThe period of first generation: 1946-1959. Vacuum tube based. 2 Second Generation ... Definition It is a type of RAM. SRAM

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COMPUTER REFRESHER FOR IBPS RRB

What is a computer?

An electronic device which is capable of receiving data in a particular form and of

performing a sequence of operations in accordance with a predetermined but variable set of procedural instructions (program) to produce a result in the form of information.

Structure of a computer

INPUT UNIT:

This unit contains devices with the help of which we enter data into computer. This unit makes link between user and computer. The input devices translate the information into the form understandable by computer.


Following are few of the important input devices which are used in a computer:

Keyboard, Mouse, Joy Stick ,Light pen, Track Ball, Scanner, Graphic Tablet

Microphone, Magnetic Ink Card Reader(MICR) ,Optical Character Reader(OCR),

Bar Code Reader, Optical Mark Reader(OMR).

The QWERTY keyboard was invented in 1875, by Christopher Latham Scholes.

A standard keyboard has 101 keys.

The Computer mouse was invented in 1960, by Douglas Engelbart

OUTPUT UNIT:

Output unit consists of devices with the help of which we get the information from computer. This unit is a link between computer and users. Output devices translate the computer's output into the form understandable by users.

Following are few of the important output devices which are used in a computer.

Monitors, Graphic Plotter, Printer

CENTRAL PROCESSING UNIT (CPU):

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

Arithmetic & Logic Unit (ALU)

Memory Unit

Control Unit

ARITEMATIC&LOGIC UNIT (ALU):


ALU is the part of a computer that performs all arithmetic computations, such as addition and multiplication and all comparison operations.

MEMORY UNIT:

Computer memory is the storage space in computer where data is to be processed and instructions required for processing are stored.

CONTROL UNIT:

This unit controls the operations of all parts of computer but 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.

CPU Special Registers

The CPU contains a number of special-purpose registers:

Instruction Register (IR): The instruction register holds the instruction currently being executed.

Memory Data Register (MDR): The memory data register (also known as the memory buffer

register or data buffer) holds the piece of data that has been fetched from memory.

Memory Address Register (MAR): The memory address register holds the address of the next

piece of memory to be fetched.


Program Counter (PC): The program counter holds the location of the next instruction to be

fetched from memory. It is automatically incremented between supplying the address of the next

instruction and the instruction being executed.

Accumulator: The accumulator is an internal CPU register used as the default location to store

any calculations performed by the arithmetic and logic unit.

Generation of Computers

Generation in computer terminology is a change in technology a computer is/was being used.

There are totally five computer generations known till date.

S.N. Generation & Description

1 First Generation

The period of first generation: 1946-1959. Vacuum tube based.

2 Second Generation

The period of second generation: 1959-1965. Transistor based.

3 Third Generation

The period of third generation: 1965-1971. Integrated Circuit based.

4 Fourth Generation

The period of fourth generation: 1971-1980. VLSI microprocessor based.

5 Fifth Generation

The period of fifth generation: 1980-onwards. ULSI microprocessor based


Types of computer:

Sr. No.

Type Specifications

1 PC (Personal Computer)

It is a single user computer system having moderately powerful microprocessor

2 WorkStation It is also a single user computer system which is similar to personal computer but have more powerful microprocessor.

3 Mini Computer It is a multi-user computer system which is capable of supporting hundreds of users simultaneously.

4 Main Frame It is a multi-user computer system which is capable of supporting hundreds of users simultaneously. Software technology is different from minicomputer.

5 Supercomputer It is an extremely fast computer which can execute hundreds of millions of instructions per second.

Charles Babbage is called the "Father" of the computer. The First mechanical computer

designed by Charles Babbage was called Analytical Engine.

World’s first Supercomputer were introduced in the 1960s, by Seymour Cray at Control

Data Corporation (CDC).

Performance of a supercomputer is measured in floating point operations per second

(FLOPS).

Supercomputer with fastest speed is NUDT Tianhe-2 manufactured by China in 2013.

PARAM 8000 is considered India's first supercomputer. It was indigenously built in 1990

by Centre for Development of Advanced Computing.


Latest Supercomputer in India developed by Indian Institute of Science, Bangalore name

SahasraT (SERC - Cray XC40) speed 901.5 FLOPS world rank 79.

Computer Hardware

Hardware represents the physical and tangible components of a computer i.e. the components that can be seen and touched.

Examples of Hardware are following:

Input devices -- keyboard, mouse etc.

Output devices -- printer, monitor etc.

Secondary storage devices -- Hard disk, CD, DVD etc.

Internal components -- CPU, motherboard, RAM etc.

Computer Software

Software is a set of programs, which is designed to perform a well-defined function. A program is a sequence of instructions written to solve a particular problem.

What is open source software?

Open source software is software whose source code is available for modification or enhancement by anyone.

Example: Linux, Apache, Firefox, MYSQL, PHP, Thunderbird

What is Closed Source Software? Closed source software can be defined as proprietary software distributed under a licensing agreement to authorized users with private modification, copying and republishing restrictions.

Example: Mac OS X, Photoshop, Windows 7, Skype, Adobe Flash Player, Internet Explorer


Types of software

Difference between application software and system software

Subject Application Software System Software Definition Application software is

computer software designed to help the user to perform specific tasks.

System software is computer software designed to operate the computer hardware and to provide a platform for running application software.

Purpose Application software is System software is computer


computer software designed to help the user to perform specific tasks.

software designed to operate the computer hardware and to provide a platform for running application software.

Purpose It is specific purpose software. It is general-purpose software. Classification Package Program,

Customized Program

Time Sharing, Resource Sharing, Client Server Batch Processing

Operating System Real time Operating

System Multi-processing Operating

System Multi-programming

Operating System Distributed Operating

System

Environment It executes as and when required.

It executes all the time in computer.

Essentiality Application is not essential for a computer.

System software is essential for a computer

Number The number of application software is much more than system software.

The number of system software is less than application software.

Operating System


An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is a vital component of the system software in a computer system.

An operating system is a program that acts as an interface between the software and the computer hardware.

It is an integrated set of specialised programs that are used to manage overall resources and operations of the computer.

It is specialised software that controls and monitors the execution of all other programs that reside in the computer, including application programs and other system software.

Relationship between Hardware and Software Hardware and software are mutually dependent on each other. Both of them must work

together to make a computer produce a useful output.

Software cannot be utilized without supporting hardware.

Hardware without set of programs to operate upon cannot be utilized and is useless.

To get a particular job done on the computer, relevant software should be loaded into the hardware

Hardware is a one-time expense.

Software development is very expensive and is a continuing expense.

Different software applications can be loaded on a hardware to run different jobs.

A software acts as an interface between the user and the hardware.

If hardware is the 'heart' of a computer system, then software is its 'soul'. Both are complimentary to each other.

MEMORY


Cache Memory Cache memory is a very high speed semiconductor memory which can speed up CPU. It is used to hold those parts of data and program which are most frequently used by CPU.

Advantages

The advantages of cache memory are as follows:

Cache memory is faster than main memory.

It consumes less access time as compared to main memory.

It stores the program that can be executed within a short period of time.

It stores data for temporary use.


Disadvantages

The disadvantages of cache memory are as follows:

Cache memory has limited capacity.

It is very expensive.

Function of different register

SI No. Name of register Function

1 Memory Address(MAR) Holds address of the active

memory location.

2 Memory Buffer(MBR) Holds information on its way to

and from memory.

3 Program Control(PC) Holds address of the next

instruction to be executed.

4 Accumulator(A) Accumulates result and data to

be operated from.

5 Instruction(I) Holds an instruction while it is

being executed.

6 Input/Output(I/O) Communicates with I/O devices.

Difference between Primary memory and Secondary memory

Primary memory Secondary memory

Speed Fast

Slow

Cost Expensive

Cheap

Capacity Low capacity Large capacity


Primary memory is divided into two subcategories RAM and ROM.

Difference between RAM and ROM

Difference between SRAM and DRAM

SRAM DRAM

Relation with

Processor

Works directly with the

processor

Not connected directly to

the processor

RAM ROM

Stands for Random Access Memory Read only memory

Use

RAM allows the computer to read

data quickly to run applications.

It allows reading and writing.

ROM stores the program

required to initially boot

the computer. It only

allows reading.

Volatility

RAM is volatile i.e. its contents are

lost when the device is powered

off.

It is non-volatile i.e.

its contents are retained

even when the device is

powered off.

Types

The two main types of RAM are

static RAM and dynamic RAM.

The types of ROM include

PROM, EPROM and

EEPROM.


Definition It is a type of RAM. SRAM

essentially uses latches

to store charge.

It is also a type of RAM. DRAM

makes use of capacitors to store

bits in the form of charge.

Speed Faster Slower

Size Bigger Smaller

Capacity Less 5 to 10 times more than SRAM

Applications Generally in smaller

applications like CPU

cache memory and hard

drive buffers

Commonly used as the main

memory in personal computers

Access Easy Harder

Power Consumption Less More

Rom has mainly three types: PROM,EPROM and EEPROM.

PROM (Programmable Read only Memory)

PROM is read-only memory that can be modified only once by a user.

EPROM (Erasable and Programmable Read Only Memory)

During programming, an electrical charge is trapped in an insulated gate region. For erasing

this charge, ultra-violet light is passed through a quartz crystal window(lid). This exposure to

ultra-violet light dissipates the charge.

EEPROM (Electrically Erasable and Programmable Read Only Memory)

The EEPROM is programmed and erased electrically. It can be erased and reprogrammed

about ten thousand times. The process of re-programming is flexible but slow.


Secondary Memory This type of memory is also known as external memory or non-volatile. It is slower than main

memory. These are used for storing data/Information permanently.

For example : Hard disk, CD-ROM, DVD etc.

Characteristic of Secondary Memory These are magnetic and optical memories

It is known as backup memory.

It is non-volatile memory.

Data is permanently stored even if power is switched off.

It is used for storage of data in a computer.

Computer may run without secondary memory.

Slower than primary memories.

Hard disk

It is used as main storage device of the computer. It uses 2-4 metallic disk (platter). The disk is

usually made of aluminum. It has the storage capacity of few mega bytes to tera byte.

CD

It stands for Compact Disk. It has storage capacity of 700 MB or approximately 90 minutes of standard audio.

Types of CD are

CD-R is a blank CD in which data can be stored once. After storing data it is converted into CD-

ROM.

CD-ROM It cannot be erased or updated

CD-RW it can be erased and used for multiple times.

DVD


It stands for Digital Versatile Disk. It has the storage capacity of 4.7GB to 17GB. Its shape and

size is similar to CD but the difference in storage capacity is due to different chemical component and data is compressed before storing.

Pen drive It is a flash memory. It is a semi-conductor memory. It is mainly used for transferring data. It has

faster read/write speed compared to magnetic memory. Pen drive has storage capacity of few

MB-GB. A pen drive is a plug and play device. A pen drive can be connected with the computer through USB port.

Computer languages

A programming language is a special language use to develop applications, scripts, or other set of instructions for computers to execute.

Machine Language

Machine language or machine code is a set of instructions executed directly by a computer's central processing unit (CPU).

Assembly Language

Assembly language is a low-level programming language for a computer or other programmable device specific to a particular computer architecture in contrast to most high-level programming languages, which are generally portable across multiple systems.

Difference between High-Level & Low-Level Language

High-level Language

Low-level languages

Learning High-level languages are easy to learn.

Low-level languages are difficult to learn.

Understanding High level languages are near to human languages.

Low-level languages are far from human languages.

Execution Programs in high-level languages are slow in execution.

Programs in low-level languages are fast in execution.

Modification Programs in high-level languages are easy to modify.

Programs in low-level languages are difficult to modify.

Uses These languages are normally used to write application programs.

These languages are normally used to write hardware programs.


Special purpose language

A special purpose language is a program language that was designed for a specific function. For example, LISP is an example of a special purpose programming language designed to create artificial intelligence.

Examples of High level languages are BASIC, COBOL, C, C++, Pascal, Prolog and JAVA

COBOL stands for Common Business Oriented Language for business data processing. Fortran: The name FORTRAN is an acronym for FORmula TRANslation, because it was

designed to allow easy translation of math formulas into code.

The C is a general-purpose, procedural, imperative computer programming language

developed in 1972 by Dennis M. Ritchie at the Bell Telephone Laboratories to develop

the UNIX operating system.

Difference between source code and objet code

S. No. Source code Object code

1 Source code is written in high-level or assembly language.

Object code is written in machine language through compilers.

2 Source code is easy to understand.

Object code is difficult to understand

3 Source code is easy to modify. Object code is difficult to modify

4 Source code contains fewer statements than object code.

Object code contains more statements than source code.

Language translator

Language translator is a program that translates a program of high level language of computer

understands only machine language. A program written in high-level or assembly language

cannot be run on a computer directly. It must be converted into machine language before

execution.


Types of translators

1. Compiler A compiler is a program that converts the instruction of a high level language into machine language as a whole.

Or,

The compiler converts the source program into machine code as a whole.

2. Interpreter An interpreter is a program that converts one statement of a program into machine at one time.

The advantage of interpreters over compilers is that an error is found immediately. So the programmer can correct errors during program development.

The disadvantage of interpreter is that it is not very efficient.

3. Assembler

An assembler is translating program that translates the instruction of a assembly language into

machine language.

Microsoft word

Word Processing Software

Word processing software is used to manipulate a text document, such as a resume or a report.

Some of the functions of word processing software include:

Creating, editing, saving and printing documents. Copying, pasting, moving and deleting text within a document. Formatting text, such as font type, bolding, underlining or italicizing. Creating and editing tables. Inserting elements from other software, such as illustrations or photographs. Correcting spelling and grammar.

Microsoft word shortcut keys:

Shortcut Description Ctrl + N Starts a new blank document Ctrl + W Close the active document Ctrl + S Save a document Ctrl + P Display the print dialog box. Ctrl + F Open find box.


Ctrl + Page Up Move to the previous edit location Ctrl + Page Down Move to the next edit location Backspace Deletes one character to the left Ctrl + Backspace Deletes one word to the left Deletes Deletes one character to the right Ctrl + Delete Deletes one word to the right Ctrl + Z Undo last action. Ctrl + Y Redo the last action performed. Ctrl + X Cut selected text. Ctrl + C Copy selected text. Ctrl + V Paste. Ctrl + A Select all contents of the page. Ctrl + B Bold highlighted selection. Ctrl + I Italic highlighted selection. Ctrl + U Underline the selected text. Ctrl + Shift + L Quickly create a bullet point. Ctrl + Shift + F Change the font. Ctrl + Shift + > Increase selected font +1pts up to 12pt and

then increase font +2pts. Ctrl + ] Increase selected font +1pts. Ctrl + Shift + < Decrease selected font -1pts if 12pt or lower; if

above 12, decreases font by +2pt. Ctrl + [ Decrease selected font -1pts. Ctrl + <left arrow> Moves one word to the left. Ctrl + <right arrow> Moves one word to the right. Ctrl + <up arrow> Moves to the beginning of the line or

paragraph. Ctrl + <down arrow> Moves to the end of the paragraph. Ctrl + Shift + F6 Switches to another open Microsoft Word

document. Ctrl + Shift + F12 Prints the document. F1 Open Help. F7 Spellcheck and grammar check selected text

or document. F12 Save As. Shift + Alt + D Insert the current date. Shift + Alt + T Insert the current time.

Computer network and security

Difference between Internet and Intranet.

Internet

1. Internet is network of Computers which is open for all.


2. Internet itself contains a large number of intranets. 3. Unlimited number of users. 4. Visitors traffic is unlimited. 5. Contains unlimited source of information. 6. Collection of various LANs, WANs and MANs.

Intranet

1. Intranet is network of Computers designed for a specific group of users. 2. Intranet can be accessed from Internet but with restrictions. 3. Limited number of Users. 4. Limited visitors traffic. 5. Contains only specific group purpose information. 6. Mostly any of LAN or MAN or WAN.

Difference Between LAN, MAN and WAN

LAN

1. LAN (Local Area Network) is a group of computers and other network devices which are connected together.

2. All the devices that are part of LAN are within a building or multiple building. 3. LAN network has very high speed mainly due to proximity of computer and

network devices. 4. LAN connection speeds can be 10Mbps or 100Mbps or 1000Mpbs also. 5. LAN uses Guided Media

MAN

1. MAN ((Metropolitan Area Network) is a larger network of computers and other network devices which are connected together usually spans serveral buildings or large geographical area.

2. All the devices that are part of MAN are span across buildings or small town. 3. MAN network has lower speed compared to LAN. 4. MAN connection speeds can be 10Mbps or 100Mbps. 5. MAN uses Guided Media or Unguided media.

WAN

1. WAN (Wide Area Network) is a group of computers and other network devices which are connected together which is not restricted to a geographical location. Internet is WAN

2. All the devices that are part of WAN have no geographical boundaries.


3. WAN speed varies based on geographical location of the servers. WAN connects several LANs

4. WAN connection speeds can be 10Mbps or 100Mbps. 5. WAN mainly uses Guided Media or Unguided media. Its long distance communications,

which may or may not be provided by public packet network.

Open Systems Interconnection (OSI) model OSI (Open Systems Interconnection) is reference model for how applications can

communicate over a network. The purpose of the OSI reference model is to guide vendors and developers so the

digital communication products and software programs they create will interoperate, and to facilitate clear comparisons among communications tools.

There are seven layers in the OSI model, each having a different task.

Difference Between Virus and Worm


Virus Worm How does it infect a computer system?

It inserts itself into a file or executable program.

It exploits a weakness in an application or operating system by replicating itself.

How can it spread? It has to rely on users transferring infected files/programs to other computer systems.

It can use a network to replicate itself to other computer systems without user intervention.

Does it infect files? Yes, it deletes or modifies files. Sometimes a virus also changes the location of files.

Usually not. Worms usually only monopolize the CPU and memory.

whose speed is more? Virus is slower than worm. Worm is faster than virus.

Eg.The code red worm affected 3 lakhs PCs in just 14 Hrs.

Definition

The virus is the program code that attaches itself to application program and when application program run it runs along with it.

The worm is code that replicate itself in order to consume resources to bring it down.

Trojan horse

In computers, a Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data in such a way that it can get control and do its chosen form of damage, such as ruining the file allocation table on your hard disk.

What is Anti-Virus Software?

Anti-virus software is a program or set of programs that are designed to prevent, search for, detect, and remove software viruses, and other malicious software like worms, trojans, adware, and more.

Documents

COMPUTER REFRESHER FOR IBPS RRB - bsc4success · PDF fileThe period of first generation: 1946-1959. Vacuum tube based. 2 Second Generation ... Definition It is a type of RAM. SRAM