MCA

A Probabilistic Approach to Micropayment
A cognitive radio approach for using of virtual unlicensed spectrum
AMD Processors
ARGUMENTED VIRTUAL REALIT
ARM architecture
ARRAS AND SENSORS
ATM networks
AUGMNETED VIRTUAL REALIT
Acid rains
Advanced Encryption Standard
Advanced Queue Management Techniques
Agent Mediated E-commerce
Agile Software development
Analysing Software Life Cycle of Different Program Paradigm
Ant Colony optimization for routing in Mobile and Adhoc Networks
Antimeter
Application of ANN in Data Mining of Medical Images
Application of Genetic Algorithms in Network routing
Applications of Graph Theory to Metabolic Pathways
Applications of Soft Computing in Medical Image Analysis
Applications of speech recognition
Approximate string matching for Music retrieval
Archiever Analyzer
Artificial Intelligence in Machines
Artificial Neural Networks
Aspect-oriented programming (Aop
Aspects of Database Security and Program Security
Attacks on Smart Cards
Augmented Reality
Authentication
Authentication and Key Agreement (AKA
Authoring environments for open source courseware
Auto-pilots
Automatic number plate recognition
Autonomic Computing
Autonomic computing
BAR CODES
BARCODES
BEANS
BIO METRICS
BLOW FISH
BLU-RA DISC
BLUE RAY DISKS
BRAIN FINGER
BRAIN FINGER PRINT TECHNOLOG
BRAIN FINGER PRINT TECHNOLOGY
BRIAN GATE TECHNOLOGY
Backup and Recovery planning
Bandwidth estimation in broadband access networks
Bio Telemetry
Bio metrics IRIS technique
Bio-Medical Instrumentation and Signal analysis
BioComputers
Biometric Secuirty
Biometric Technology
Biometrics
Bionetric Authentication
Bit And Bytes
Bit and bytes
Blogs & their Creation
Blue Ray
Blue Tooth Technology
Blue-ray disk
Bluetooth technology
Botnet
Brain computer interface
CASP
COMPLIERS
CRPTOGRAPHY AND N/W SECURITY
CRYONICS
CRYPTOGRAPHY
Capacity of Ad-hoc Wireless Networks
Captchas
Cd,dvd,ird
Cell phones
Channel Allocation Algortihms for Mobile Telephony
Chess Algorithm
Choreography
Classification, Clustering and Application in Intrusuion Detection System
Classification, Clustering and their Application for Damage Detection in Mechanical Structures
Cluster computing
Clustering
Co-operative LINUX
Collaborative Mobile Environments
Comparative study on Authoring Tools
Compressed Domain Processing And Video Information System
Computational Geometry in Drug Design
Computational Intelligence and Linguistics
Computational Photography
Computational neuroscience
Computer Forensics
Computer hardware
Computer peripherals
Computer vision
Concurrent Programming and Parallel distributed O.S.
Content Management
Cooperative Adaptive Cruise Control
Cross Platform Component Object Model
Crusoe Processors
Cryogenic Processor
Cryptography
Cryptography and steganography
Curl: A Gentle Slope Language For The Web
Cyber Crime and Security
Cyborgs
DATA WARE HOSUING & MINING
DIGITAL MOVIES
DISTRUBUTED COMPUTING
DNA Based computer
DNA Computing
DRUG DISCOVERY
DYNAMIC SOURCE ROUTING PROTOCOL
Data Management in Sensor Networks
Data Mining and Data Warehousing
Data Mining concepts & Models
Data Pre Processing
Data Warehouse
Data mining through Active Learning
Data over Cable System (DOCSIS
Data warehousing
DataBase Migration
DataWareHosuing
Database Security
Dataflow machines
Datagram Congestion Control Protocol (DCCP
Dataset Query algorithms in Streaming Mining
Datbase management
Determining Global States of Distributed Systems
Digital Imaging
Digital Jewellery
Digital Media Broadcasting
Digital Rights Management
Digital Signal Processing and their applications
Digital Video Editing
Digital Visual Interface
Digital audio
Distributed Computing
Distributed Firewalls
Distributed Garbage Collection
Distributed and Parallel Computing
Distributed computing
Distributed database management system
Dna computing
Dual Energy X-ray Absorptiometry
Dynamic resource allocation in Grid Computing
Dynamic spectrum access
E-Commerce
E-MINE: A novel web mining approach
E-wallet
ELECTRONIC CARDIO GRAM
ELLICA
Earning Online Money
Earth Simulator- Fastest Supercomputer
Efficiency / Comparative study of routing schemes in event based systems
Elliptical Curve Cryptography(ECC
Embedded Configurable Operating system
Embedded Linux
Embedded systems
Embedded systems and vlsi an architectural approach to reduce leakage energy in memory
Embedded web server for remote access
Embeded Systems
Emergency Health Care System
Emerging trends in robotics using neural networks
Encrypted Hard disks
Encrypted Text chat Using Bluetooth
Energy Efficient query Optimization
Enery efficiency in Wireless sensor networks
Enterprise Security
Epsilon nets and transversal of hypergraphs
Ethernet
Ethical Hacking
Ethical hacking
Etl tools(informatica)
Evolution of computers
Evolutionary Programming
Ext3 Filesystem
FIBER CHANNELS
Facial Recognition System
Fault Tolerance in Virtual Machine Environments
Faultolerant Routing in Mobile Ad-Hoc Network
Fiber optic communication
Financial Forecasting
Fine Grained DataBase Security
Fine-grained Access Control in Databases
Fingerprint recognition system by neural networks
Firewalls
Flexible CRT Displays
Fluorescent Multilayer Disc (FMD
Fluorescent Multilayer Optical Data Storage
Forecasting
Forecasting using Double Exponential Smoothing Method
Form Processing
Form Wizard
Franchise Mgnt System
Frequent ItemSet Mining
Fusion Memory
Future Programming Techniques and Concepts
Future of Satellite Communication
Future of business Computing
Future of the internet
Fuzzified Computer-Automated Crane Control System
Fuzzy Logic
GABOR Wavelet
GAIT RECOGNITION
GIMP
GLUCO METER
GRASSHOPPER Operating System
GSM Security And Encryption
Generic algorithm
Genetic Algorithm
Genetic Programming
Geographic Versatile Dist
Geometric Invariants in Biological Molecules
Gesture recognition
Gigabit networking
Global Positioning System
Global System for Mobiles
Global positioning response system
Globalization
Gnu Emacs
Google or Yahoo Case Study
Graphical Processing Unit
Grid Computing
Grid Data Farm for Petascale
Grid computing
HACKERS
HAVi: Home Audio Video Interoperability
HIGH SPEED LANS
HOLOGRAPHIC MEMORY
HONE POTS
HONEY POTS
HUMAN AREA NETWORK
HYPER THREAD TECHNOLOGY
Hackers prospectivs
Hacking
Hapics
High Altitude Aeronautical Platforms
High Performance Clusters
High Performance Computing
High Performance DSP Architectures
High Speed Data In Mobile Networks
Holographic Memory
Holographic Versatile Disc
Holt-Winters technique for Financial Forecasting
HomeRF- localized wireless technology optimized for the home environment
Honeypots
How E-learning Works
Hyper-Threading Technology
IDMA The Future of Wireless Technology
INFORMATION SECURITY
INTERFACES
IP SPOOFING
IPODS
Image compression
Image processing and applications
Improving tcp performance over mobile ad hoc networks
Information Extraction from structured & Semi-structured data
Information Extraction modes & techniques
Integrating Structural Design and Formal Methods in RealTime System Design
Integration of Parallel Database in a Service Oriented Architecture
Intel MMX Technology
Intelligent Patient Monitoring System
Intelligent RAM : IRAM
Inter-Operabilty of 802
Internet Cryptopraphy
Internet Networking
Internet Searching
Internet Telephony
Internet version 2
Interupts
Introduction to LaTeX
Introduction to Speech Recognition
Ipod
Iris scanning
Issues in Middleware for Pervasive Computing
J2EE Security
JIRO Java-based technology
Java Class Loader
Java Cryptography Architecture (JCA
Java Messaging Service (JMS
Java Security
Kerberos
Kinetic data structuring
Knowledge discovery and Data Mining
LAN PROTOCOL
LAN PROTOCOL ARCHITECTURE
LOC technology (Lab On a Chip
Layered versioning for software configuration management
Leave Mgnt System
Light Pen
Light-trails
Lixto suite
Lucid Linx
MAC address
MAGIC SQUARES
MAIN FRAMES
MANET:-The Art of Networking without a Network
MPEG-7
Magnetic RAM
Mail server Management
Main memory databases
Management Information System
Managing Data with emerging technologies
Matlab (matrix lab)
Media gateways
Mesh Based Geometric data processing
Methods in virtual networking
Methods in virtual private networks
Micro Hard disk Drives
Micro Mouse
Micro Total analysis systems
Micro chip production using extreme uv lithography
Microcontroller Based Automation
Microcontroller Based Power Theft Identification
Middleware architecture for Pervasive computing
Middleware for Sensor Networks
Middleware for Wireless Sensor Networks
Middleware in Embedded Systems
Middleware in embedded systems
Mining Document Streams
Mining the Web: Searching, Integration and Discovery
Mobile Casts
Mobile Computing
Mobile Infrastructure Management
Mobile Library Management
Mobile Networking
Mobile Paradigm
Mobile ad hoc network
Mobile agent
Mobile communication
Molecular Keypad Lock
Multi Protocol Label Switching
Multi-Relational Data Mining
Multi-application Framework for Smart Cards
Multicast Congestion Control
Multicast Routing
Multimedia
Multimedia Broadcasting via Satellite
Multiple Domain Orientation
Multiple client’s communication
NANO TECHONOLGY
NETWORK SECURITY
NVSRAM- Non Volatile Static RAM
Nano Ring Memory
Nano computing
Nano-technology and application
Narrow Band and Broad Band ISDN
Native Command Queuing (NCQ
Natural Language Processor
Near Filed Communication (NFC
Netowork Security
Network Accelerators
Network Anomaly
Network Management and Security
Network Modeling and Simulation
Network security with cryptography
Neural networks and applications
New Age Graphics
New Dimension of Data Security using Neural Networks and Numerical Functions
New storage strategy = Disk -Disk -Tape Back up
Night Vision Technology
Nonvolatile Flash Memory
OOPS CONCEPTS
ORACLE DATABASE 10g
Object Persistence
Object oriented technologies
Online software Distribution
Ontological Relation Discovery
Open Source Technology
Open ‘ssh’
OpenGL-application programming interface
Operating systems
Optical Disc Data Security
Optical canoflague
Optical networking
Optimization of Protocol Stack for wireless networks
Oracle RDBMS
Orthogonal Frequency Division Multiplplexing
Ovonic Unified Memory
Packet Interception
Parallel Computations
Parallel Computing In Remote Sensing Data Processing
Parallel computing
Parasitic computing
Peer to Peer and Overlay Networks
Peer to peer Networking
Pen Drive
Performance Evaluation
Performance Evaluation of IEEE 802
Personal Mass Media Blogging, Syndication, Podcasting, and Vidcasting
Personal Satellite assistant Systems
Personel Digital assistance
Pervasive computing
Plasma Displays
Plasmonics
Pluggable Authentication Modules (Pam
PolyBot Modular, self-reconfigurable robots
Polymer Memory
Porting Device Drivers For The Solaris
Power Line Networking
Proactive Anomaly Detection
Proactive Network Anomaly Detection
Proactive computing
Probabilistic I/o Automata
Public Key Encryption And Digital Signature
QOS in software server Firewalls
QoS in Networking using active Networks
QoS in VoIP
QoS in Wireless LANs
Quad core Module technology
Quality of Service Routing in computer networks
Quality of service in Differentiated Service Architecture
Quantum computing
Quantum teleportation
Query Based Fine-grained PageRank
Query Optimization
Query Processing on Data Streams
RED TACTON
RFID : Comparative study of Collision Resolution Protocols
RFID Security
Radio Astronomy
Real Time Operating Systems on Embedded ICs
Real Time Speech Translation
Real time communication in wireless sensor networks
Recognition of VoIP Speech
Reconfigurable Hardware in Wireless communication
Reconfigurable computing
Recovery in Main Memory Databases
Red Tacton
Relational Data Mining
Reliable Multicast
Reliable and Fault Tolerant Routing on Mobile Ad Hoc Network
Rendering Maths on web with Java Swing
Revolutions in the Operating System and Servers
Robocode
Root cause Localization and analysis of faults[Autonomic Computing]
Routing in Sensor Networks
Ruby on Rails RoR
S/w life cycle/affiliated programs
SALT (Speech Application Language Tags
SERVELTS
SIMPUTERS
SMART CARDS
SMART QUILL
SPINTRONICS
SPYWARE
SSL-TLS
SUNSPOT (wireless sensor network
SUPER COMPUTER
Samba Fileserver(38
Sand Box Technology
Satellite Networks
Satellite communication
Scheduling algorithm
Scheduling in Embedded Multiprocessors
Search Engine
Search Engine Optimisation
Search algorithm
Search for extra terrestrial intelligence using satellite communication
Seasonal and Adaptive Forecasting
Secure Computing
Secure Database Service
Secure Socket Layer (SSL
Security Issues In GRID COMPUTING
Security Issues in Wireless Networks
Security On Wireless LAN Adaptive cruise control
Security of Open-Source Software
Security threats in the World Wide Web
Semi Supervised Learning using Gaussian Process
Semi-supervised Learning using Graph Kernels
Sensor Networks
Sensor fusion for video surveillance
Serial ATA (SATA
Serial Attached SCSI
Servelts
Server side Java
Server virtualization
Session Initiation Protocol (SIP
Signal Integrity Fundamentals for Digital Design
Signal Processing for Networking
Site Search Engine
Smart Card Standards
Smart Dust
Sniffers
Soft computing
Software Architecture Analysis
Software Code Security
Software Testing & Quality Assurance
Software advances in wireless communication (Cognitive Radio, Dynamic spectrum Access, etc.
Software model checking
Spatial DataMining
Spectral Methods for Graph Partitioning
Spin monics
Split Range Synchronization
Statistical Forecasting
Stealth Virus
Steganography. The art of hiding information
Stereoscopic Projection Systems
Storage Farms
Storm botnet
Struts Integration
Study of TGREP
Super computer
Surface-conduction Electron-emitter Display (SED
Symbian OS
Synchronous Optical Networking
TDMA implementation for QoS routing in Ad Hoc Networks
TESTING METHODS
TETRA-Terrestrial Enhanced Trunked Radio
TOUCH SCREEN SSTEM
Tablet PC
Tablet-pc
Tape Drive Technologies LTO
Task Management
Techniques for analysis, verification, validation of digital systems
Techniques to aid property specification in Model Checking
Technotask management
Telephony Routing over IP
Teleportation
Text Classification
Text Classification Using Semi-supervised and Active Learning
The Architecture of a Moletronics Computer
The MBMS
The Mbone And Multicasting
Third Generation
Time Complexity
Torents
Touch Screen
Touch screen technology
Tracking and Positioning of Mobiles in Telecommunication
Transient Stability Assessment using Neural Networks
Trends in Compiler Construction
Trends in Mobiles & PC’s
Trusted Network Connect (TNC
Turbo Codes
Twd radar satellite communications
UMA (Unlicensed Mobile Access
USB Tape Drives
Ubiquitous computing
Unbiquitos Smart Homes
Unified Communication
Uniprocessor Virtual Memory Without TLBS
Using Regular Expressions In java
VHDL (VHSIC Hardware Description Language
VIRTUAL REALITY
VOIP Over Wireless LAN
VOIP Security
VQ In Converging Telephony And Ip Networks
Vertical Cavity Surface Emitting Laser
Video conference
Virtual Keyboards
Virtual Network Computing
Virtual P.C.
Virtual Private Networks(VPNs)
Virtual Reality
Virtual memory
Virtual networking
Virtualization Technology
Viruses and Worms
Visual Neuro Prosthetics
Visualization and Computer Graphics
VoIP in mobile phones
Voice Over Internet Protocol
Voice Portals
Voice Roaming
Voice Routing over IP Telephony
WATERFALL MODEL
Watermarking Digital Audio
Wearable Computers
Web Data Management
Web Designing with HTML
Web Search Results' Ranking: PageRank, HITS and Related Work
Web Spam
Web Technology
Web browsers
Web servers
Wi- Fi Technology
Wi-Fi (802.11b
Wimax
Windows Vista
Wireless Application Protocol
Wireless Applications
Wireless Connectivity for Rural Areas
Wireless MAN
Wireless Markup Language(WML
Wireless Security
Wireless Technologies (bluetooth, 802.11x, IRDA
Wireless communication system
Wireless sensor network
Wireless technology
Working of E-Mail
X-Internet
X-By-Wire System , Communication Bus perspective
ZFS File system
eXtensible Bindings Language (XBL
iSCSI: The future of Network Storage
membrane computing
multi-wordnets
multimedia-oriented web based instructional system

Microsoft kinect Sensor(2011 Technology)

Memristor

Bladeless Wind Turbine

Electric Field From Insulated Electrodes

Low Iron Glass - Double Glaze for Greenhouse

Windows Azure Cloud

Commercial space exploration

Improving the Reach of Healthcare Through Mobile Technology

WikiBhasha

Advances Artificial Intelligence

Wireless 'White Space' Frequencies

Application Outsourcing: The Next Big Thing on the Internet

Dress Reacts With Lights In Response To Air Quality

Contact Lenses That Change Color To Alert Diabetics of Glucose Levels

Spinning mirror light-field display

New Low Cost Ways to Compress Air

human fly with wings

Self-Inflating Tires

Electrons in plasma for electricity

Hydrogel lenses

Military exoskeleton prototype

Interactive 360º 3-D Holographic Displays

Microsoft's newest operating system, Windows 7

Google's +1 - content recommenation tool

Yahoo's Hadoop

Promising Invention: Paper Batteries

Google Cloud Print

Windows MultiPoint Server 2010

Windows 8(Medori)

Cellonics Technology

FinFET Technology

Intel core i9,i3,i5,i7

Browser OS

iWall - an Intelligent Public Display

Quantum teleportation

Intel Arrandale core(2010 Technology)

ARTIFICIAL EYE

Augmented Reality

Blue Eyes

Blu-Ray DVD

Brain Computer Interface

CDMA 2000 (3G)

Chameleon Chips

clockless chip

Controller Area Network

Digital Audio Broadcasting

Digital Light Processing

Digital Subscriber Line

Direct to home television (DTH

dna based computers

E- Bomb

Electromechanical Human-machine interaction

EMBEDDED

FREE SPACE OPTICS

Generic framing procedure(GFP)

GPRS

GRAPHICS PROCESSING UNIT

HAAPS

holographic memory

HVAC Duct As A Communication Channel

hyper sonic sound

hyperthread

IMAX

IMODE

INSTRUMENT LANDING SYSTEM

LED WIRELESS

LIDAR

Light Emitting Polymers

LIGHT-TREE

MEMS

Micropower Impulse Radar

Motion Capturing

NAPI

Organic Electronics

Organic Light Emitting Diodes

Plasma Antenna

Polymer memory

Power Line Networking

Q_HEAP

QC(Quantum Computing)

Radio frequency identification

SALT

Space Time Adaptive Processing

STAP

TeraHertz Transistor

The SPEEDES Qheap A Priority-Queue

Virtual key-board

Aeronautical Communications

bicmos technology

Biomagnetism

Cruise Control Devices

Crusoe processor

MEMS technology

Satellite radio

RFID TECHNOLOGY

Speed Detection of moving vehicle using speed cameras

smart dust

Ferroelectric RAM

Grid Computing

INTEL CENTRINO MOBILE TECHNOLOGY

Java Card

Linto

Liwia

Modular Computing

PARASITIC COMPUTING

space mouse

SMART SENSOR

BIOCHIPS

Animatronics

HURD

Mobile IP

PROJECT OXYGEN

Wearable Computers

Asynchronous chip

Boarder security using wins

4g wireless technology

Honeypots

TRIPWIRE

third generation of mobile phones

HANS

IP spoofing

Internet Access via Cable TV Network

Face Recognition Technology

FireWire

Param 10000

Refactoring

On-line Analytical Processing (OLAP)

Pivot Vector Space Approach in Audio-Video Mixing

MPEG-7

Adding Intelligence to Internet

Silverlight

DNA chips

Remote Administration Trojan's

Thermography

AJAX

Alternative Models Of Computation

Amorphous Computing and Swarm Intelligence

Windows DNA

Laptop Computer

Intelligent Software Agents

Self-Managing Computing

Hurd

Intel Centrino Mobile Technology

MPEG Video Compression

Survivable Networks Systems

Self Organizing Maps

Mobile IP

Iris Scanning

LWIP

Unified Modeling Language (UML)

Nanorobotics

Dual Core Processor

Cisco IOS Firewall

Socket Programming

SAM

10 Gigabit Ethernet

Tripwire

Ubiquitous Networking

Unicode And Multilingual Computing

XML Encryption

Y2K38

VoCable

Touch Screens

Tempest and Echelon

Synthetic Aperture Radar System

Unlicensed Mobile Access

IDS

IDC

SATRACK

Asynchronous Chips

Low Power UART Design for Serial Data Communication

SPECT

Satellite Radio

Light emitting polymers

Sensors on 3D Digitization

Robotic Surgery

Buffer overflow attack : A potential problem and its Implications

Smart card

Quantum Information Technology

Money Pad, The Future Wallet

Cellular Through Remote Control Switch

HVAC

Terrestrial Trunked Radio

Swarm intelligence & traffic Safety

Facility Layout Design using Genetic Algorithm

Human Computer Interface

HPJava

HDMI

H.323

Gaming Consoles

Fluorescent Multi-layer Disc

Futex

Extreme Programming (XP)

Earth Simulator

Compact peripheral component interconnect

Digital Visual Interface

corDECT Wireless in Local Loop System

Motes

Modular Computing

MiniDisc system

Migration From GSM Network To GPRS

M-Commerce

C#

IP Telephony

RPR

Broad Band Over Power Line

Rapid Prototyping

Dashboard

Code Division Duplexing

Delay Tolerant Networking

EDGE

Holographic Data Storage

Integer Fast Fourier Transform

NRAM

Orthogonal Frequency Division Multiplplexing

Ovonic Unified Memory

Pervasive Computing

RAID

Real Time Systems with Linux/RTAI

Real-Time Obstacle Avoidance

Symbian OS

Teleportation

Turbo Codes

Utility Fog

Cluster Computing

Wireless Application Protocol

Light Tree

Smart Pixel Arrays

Project Oxygen

Wearable Bio-Sensors

Mobile Virtual Reality Service

QoS in Cellular Networks Based on MPT

Wireless Fidelity

Voice morphing

Radio Frequency Light Sources

Speed Detection of moving vehicle using speed cameras

Optical Packet Switching Network

Storage Area Networks

Smart Note Taker

Crusoe Processor

Optical Satellite Communication

Optical packet switch architectures

Optical Switching

FRAM

Virtual Private Network

Clockless Chip

Layer 3 Switching

IMode

Blue Gene

Access gateways

Computer Forensics

Direct Memory Access

Crusoe

Digital Subscriber Line

Computer Memory Based on the Protein Bacterio-rhodopsin

DNA Based Computing

Free Space Optics

Freenet

Fiber Distributed Data Interface

Dynamic Virtual Private Network

Introduction to the Internet Protocols

Graphic processing Unit

High Altitude Aeronautical Platforms

Aspect-oriented programming (Aop)
Intel MMX Technology

Hyper-Threading technology

IMAX

Brain-Computer Interface

InfiniBand

Multicast

Inverse Multiplexing

Blue Tooth

Holographic Memory

Jini Technology

Bio-metrics

Magnetic Random Access Memory

Intrution Detection System

Multiterabit Networks

Neural Networks And Their Applications

Quantum Computers

Small Computer System Interface

OpenRAN

Quadrics Interconnection Network

Plan 9 Operating System

Structured Cabling

Quantum Cryptography

Speech Application Language Tags


Real- Time Systems and Real- Time Operating Systems

Parallel Computing In India

Steganography

Virtual LAN Technology

Artificial Neural Network (ANN)

Tele-immersion

VHDL

Blue Eyes

Voice Over Internet Protocol

The Tiger SHARC processor

Autonomic Computing

Wearable Computers

Voice Portals

Tamper Resistance

CGI Programming

DRM Software Radio

Firewalls

Handheld Computers

Modems and ISDN

Optical Free Space Communication

Planar Separators

Wireless Internet

DVD Technology

MPEG-4 Facial Animation

Internet Telephony Policy in INDIA

PON Topologies

Smart Cards

Surround Systems

TCPA / Palladium

Trustworthy Computing

Sense-Response Applications

Optical Computer

Graph Separators

Extended Mark Up Language

Cellular Communications

Virtual Instrumentation

Voice Quality

Cable Modems

Dynamic Memory Allocation

Optical Mouse

Generic Framing Procedure

Dynamic Cache Management Technique

Ethernet Passive Optical Network

Synchronous Optical Networking

Development of the Intenet

Design and Analysis of Algoritms

Infinite Dimensional Vector Space

Instant Messaging

Optical Fibre Cable

GSM

Ambiophonics

Palladium

Computer Viruses

Third Generation

Sixth Sense

Object Oriented Concepts

Night Vision Technology

TCP/ IP

Dynamic Synchronous Transfer Mode

Integrated Voice and Data

Java Servlets

Smart Quill

Spam Assassin

Stereoscopic Imaging

Zigbee

Ultra-Wideband

Home Networking

Internet Protocol Television

Bacterio-Rhodopsin Memory

Blade Servers

Digital Cinema

Holographic Versatile Disc

Itanium Processor

Local Multipoint Distribution Service

Network Attached Storage

Night Vision Technology

Opera (web browser)

Parasitic Computing

Performance Testing

Java Ring

RD RAM

GSM Security And Encryption

Fast Convergence Algorithms for Active Noise Controlin Vehicles

3G vs WiFi

Body Area Network

Data Security in Local Network using Distributed Firewalls

Computerized Paper Evaluation using Neural Network

Bluetooth Based Smart Sensor Networks

Laser Communications

Multiple Domain Orientation

Industrial Applications using Neural Networks

Implementation Of Zoom FFT

Image Processing

Virtual keyboard

Transient Stability Assessment using Neural Networks

Tracking and Positioning of Mobiles in Telecommunication

Timing Attacks on Implementations

Prototype System Design for Telemedicine

Optical Networking and Dense Wavelength Division Multiplexing

Optical Burst Switching

Image Processing & Compression

Cyberterrorism

Ipv6 - The Next Generation Protocol

Driving Optical Network Evolution

Cellular Neural Network

Radio Network Controller

Digital Audio Broadcasting

Significance of real-time transport Protocol in VOIP

Space Mouse

Resilient Packet Ring Technology

3D Password

Wireless Networked Digital Devices

Design of 2-D Filters using a Parallel Processor Architecture

Hyper Transport Technology

CorDECT

Storage Area Network

High Performance DSP Architectures

Smart Dust

MANET

Biometrics Based Authentication

Software-Defined Radio

Digital Video Editing

D-Blast

Aeronautical Communication

Gigabit Ethernet

Wisenet

Digital Light Processing

Free Space Laser Communications

Millipede

AC Performance Of Nanoelectronics

4G Wireless Systems

Blu Ray Disc

Smart Fabrics

Daknet

Conditional Access System

SyncML

High Performance DSP Architectures

Short Message Service (SMS)

Worldwide Inter operatibility for Microwave Access

64-Bit Computing

Bio-Molecular Computing

1.What do you mean by data communication?
Ans: It is the exchange of data between two devices via some form of transmission medium such as wire cable. The communicating system must be part of a communication system made up of a combination of hardware and software. The effectiveness of a data communication system depends on three fundamental characteristics: delivery, accuracy and timeliness.

2.What is simplex?
Ans: It is the mode of communication between two devices in which flow of data is unidirectional. i.e. one can transmit and other can receive. E.g. keyboard and monitor.

3.What is half-duplex?
Ans: It is the mode of communication between two devices in which flow of data is bi-directional but not at the same time. ie each station can transmit and receive but not at the same time. E.g walkie-talkies are half-duplex system.

4.What is full duplex?
Ans: It is the mode of communication between two devices in which flow of data is bi-directional and it occurs simultaneously. Here signals going in either direction share the capacity of the link. E.g. telephone

5.What is a network?
Ans: It is a set of devices connected by communication links. A node can be a computer or any other device capable of sending and/or receiving data generated by other nodes on the network.

6.What is distributed processing?
Ans: It is a strategy in which services provided by the network reside at multiple sites.

7.What is point to point connection?
Ans:It provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between the two devices e.g. when we change the TV channels by remote control we establish a point to point connection between remote control and TV control system.

8.What is multipoint connection?
Ans: In multipoint connection more than two specific devices share a single link. Here the capacity of the channel is shared either separately or temporally.

9.What is a topology?
Ans: Topology of a network is defined as the geometric representation of the relationship of all the links and linking devices (node) to one another. Four basic topologies are star, bus, ring and mesh. Star – Here each device has a dedicated point to point link only to a central controller called hub. Bus -It is multipoint. One long cable acts as a backbone to link all the devices in the network. Ring -Here each device has a dedicated point to point connection only with the two devices on either side of it. Mesh -Here every device has a dedicated point to point link to every other device.

10.Define LAN, MAN and WAN.
Ans: LAN- A local area network (LAN) is a privately owned and links the devices in a single office, building or campus. It allows resources to be shared between personal computers and work stations. MAN- A metropolitan-area network (MAN) spreads over an entire city. It may be wholly owned and operated by a private company, eg local telephone company. WAN – A wide area network (WAN) provides long distance transmission of data, voice, image and video information over large geographic areas that comprise a country, a continent or even whole world.

11.Define internet?
Ans: It is a network of networks.

12.What is a protocol?
Ans: It is a set of rules that governs data communication. A protocol defines what is communicated, how it is communicated, and when it is communicated. The key elements of protocol are syntax, semantics and timing.

13.What is TCP/IP protocol model?
Ans: It is a five layered model which provides guidelines for the development of universally compatible networking protocols. The five layers are physical, data link, network, transport and application.

14.Describe the functions of five layers?
Ans: Physical- It transmits raw bits over a medium. It provides mechanical and electrical specification. Data link- It organizes bits into frames. It provides hop to hop delivery. Network-It moves the packets from source to destination.It provide internetworking. Transport-It provides reliable process to process message delivery and error recovery. Application-It allows ti access to network resources.

15.What is ISO-OSI model?
Ans: Open Systems Interconnection or OSI model was designed by the International Organization for Standardization (ISO) .It is a seven layer model. It is a theoretical model designed to show how a protocol stack should be implemented. It defines two extra layers in addition to TCP/IP model. Session -It was designed to establish, maintain, and synchronize the interaction between communicating system. Presentation-It was designed to handle the syntax and semantics of the information exchanged between the two systems. It was designed for data translation, encryption, decryption, and compression.

16. What is multiplexing?
Ans: Multiplexing is the process of dividing a link, the phycal medium, into logical channels for better efficiency. Here medium is not changed but it has several channels instead of one.

16.What is switching?
Ans: Switching in data communication is of three types Circuit switching Packet switching Message switching

17.How data is transmitted over a medium?
Ans: Data is transmitted in the form of electromagnetic signals.

18. Compare analog and digital signals?
Ans: Analog signals can have an infinite number of values in a range but digital signal can have only a limited number of values.

19.Define bandwidth?
Ans: The range of frequencies that a medium can pass is called bandwidth. It is the difference between the highest and lowest frequencies that the medium can satisfactorily pass.

20.What are the factors on which data rate depends?
Ans: Data rate ie.how fast we can send data depends upon i) Bandwidth available ii) The levels of signals we can use iii) The quality of the channel (level of noise)

21.Define bit rate and bit interval?
Ans: Digital signals are aperiodic.so instead of using period and frequency we use bit interval and bit rate respectively.Bit interval is the time required to send one single bit.Bit rate is the number of bit intervals per second.

22.What is Nyquist bit rate formula?
Ans: For a noiseless channel, the Nyquist bit rate formula defines the theoretical maximum bit rate Bitrate=2* Bandwidth*log2L Where Bandwidth is the bandwidth of the channel L is the number of signal level used to represent the data Bitrate is the bit rate in bits per second.

23.Define Shannon Capacity?
Ans: Shannon Capacity determines the theoretical highest data rate foe a noise channel. Capacity= Bandwidth * log2 (1+SNR) Bandwidth is the bandwidth of the channel.
SNR is the signal to noise ratio, it is the statical ratio of the power of the signal to the power of the noise. Capacity is the capacity of the channel in bits per second

24.What is sampling?
Ans: It is the process of obtaining amplitude of a signal at regular intervals.

25.Define pulse amplitude modulation?
Ans: It is an analog to digital conversion method which takes analog signals, samples it and generates a series of pulse based on the results of the sampling. It is not used in data communication because the series of pulses generated still of any amplitude. To modify it we use pulse code modulation.

26.Define pulse code modulation?
Ans: Pulse code Modulation modifies pulses created by PAM to create a completely digital signal. For this PCM first quantizes the PAM pulse. Quantization is the method of assigning integral values in a specific tange to sampled instances.PCM is made up of four separate processes: PAM, quantization, binary encoding and line encoding.

27.What is Nyquist Theorem?
Ans: According to this theorem, the sampling rate must be at least 2 times the highest frequency of the original signal.

28.What are the modes of data transmission?
Ans: Data transmission can be serial or parallel in mode In parallel transmission, a group of bits is sent simultaneously, with each bit on a separate line.In serial transmission there is only one line and the bits are sent sequentially.

29.What is Asynchronous mode of data transmission?
Ans: It is a serial mode of transmission. In this mode of transmission, each byte is framed with a start bit and a stop bit. There may be a variable length gap between each byte.

30.What is Synchronous mode of data transmission?
Ans: It is a serial mode of transmission.In this mode of transmission, bits are sent in a continuous stream without start and stop bit and without gaps between bytes. Regrouping the bits into meaningful bytes is the responsibility of the receiver.

31.What are the different types of multiplexing?
Ans: Multiplexing is of three types. Frequency division multiplexing and wave division multiplexing is for analog signals and time division multiplexing is for digital signals.

32.What is FDM?
Ans: In frequency division multiplexing each signal modulates a different carrier frequency. The modulated carrier combines to form a new signal that is then sent across the link. Here multiplexers modulate and combine the signal while demultiplexers decompose and demodulate. Guard bands keep the modulating signal from overlapping and interfering with one another.

32.What is TDM ?
Ans: In TDM digital signals from n devices are interleaved with one another, forming a frame of data. Framing bits allow the TDM multiplexer to synchronize properly.

33.What are the different transmission media?
Ans: The transmission media is broadly categorized into two types i)Guided media(wired) i)Unguided media(wireless)

34.What are the different Guided Media?
Ans: The media which provides a conduct from one device to another is called a guided media. These include twisted pair cable, coaxial cable, and fiber-optic cable.

35.Describe about the different Guided Medias.
Ans: Twisted pair cable consists of two insulated cupper wires twisted together. It is used in telephone line for voice and data communications. Coaxial cable has the following layers: a metallic rod-shaped inner conductor, an insulator covering the rod, a metallic outer conductor (shield), an insulator covering the shield, and a plastic cover.Coaxial cable can carry signals of higher frequency ranges than twisted-pair cable. Coaxial cable is used in cable TV networks and Ethernet LANs.Fiber-optic cables are composed of a glass or plastic inner core surrounded by cladding, all encased in an outer jacket.Fiber-optic cables carry data signals in the form of light. The signal is propagated along the inner core by reflection. Its features are noise resistance, low attenuation, and high bandwidth capabilities. It is used in backbone networks, cable TV nerworks, and fast Ethernet networks.

36.What do you mean by wireless communication?
Ans: Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is referred as wireless communication. Here signals are broadcaster through air and thus available to anyone who has a device to receive it.

37.What do you mean by switching?
Ans: It is a method in which communication devices are connected to one another efficiently. A switch is intermediary hardware or software that links devices together temporarily.

38.What are the switching methods?
Ans: There are three fundamental switching methods: circuit switching, packet switching, And message switching.In circuit switching, a direct physical connection between two devices is created by space division switches, time division switches or both. In packet switching data is transmitted using a packet switched network. Packet switched network is a network in which data are transmitted in independent units called packets.

39.What are the duties of data link layer?
Ans: Data link layer is responsible for carrying packets from one hop (computer or router) to the next. The duties of data link layer include packetizing, adderssing, error control, flow control, medium access control.

40.What are the types of errors?
Ans: Errors can be categorized as a single-bit error or burst error. A single bit error has one bit error per data unit. A burst error has two or more bits errors per data unit.

41.What do you mean by redundancy?
Ans: Redundancy is the concept of sending extra bits for use in error detection. Three common redundancy methods are parity check, cyclic redundancy check (CRC), and checksum.

42.Define parity check.
Ans: In parity check, a parity bit is added to every data unit so that the total number of 1s is even (or odd for odd parity).Simple parity check can detect all single bit errors. It can detect burst errors only if the total number of errors in each data unit is odd.In two dimensional parity checks, a block of bits is divided into rows and a redundant row of bits is added to the whole block.

43. Define cyclic redundancy check (CRC).
Ans: C RC appends a sequence of redundant bits derived from binary division to the data unit. The divisor in the CRC generator is often represented as an algebraic polynomial.

44. What is hamming code?
Ans: The hamming code is an error correction method using redundant bits. The number of bits is a function of the length of the data bits. In hamming code for a data unit of m bits, we use the formula 2r >= m+r+1 to determine the number of redundant bits needed. By rearranging the order of bit transmission of the data units, the hamming code can correct burst errors.

45.What do you mean by flow control?
Ans: It is the regulation of sender’s data rate so that the receiver buffer doesn’t become overwhelmed.i.e. flow control refers to a set of procedures used to restrict the amount of data that the sender can send before waiting for acknowledgement.

46.What do you mean by error control?
Ans: Error control refers primarily to methods of error detection and retransmission. Anytime an error is detected in an exchange, specified frames are retransmitted. This process is called automatic repeat request (ARQ).

47.Define stop and wait ARQ.
Ans: In stop and wait ARQ, the sender sends a frame and waits for an acknowledgement from the receiver before sending the next frame.

48.Define Go-Back-N ARQ?
Ans: In Go-Back-N ARQ, multiple frames can be in transit at the same time. If there is an error, retransmission begins with the last Unacknowledged frame even if subsequent frames arrived correctly. Duplicate frames are discarded.

49.Define Selective Repeat ARQ?
Ans: In Selective Repeat ARQ, multiple frames can be in transit at the same time. If there is an error, only unacknowledged frame is retransmitted.

50.What do you mean by pipelining, is there any pipelining in error control?
Ans: The process in which a task is often begun before the previous task has ended is called pipelining. There is no pipelining in stop and wait ARQ however it does apply in Go-Back-N ARQ and Selective Repeat ARQ.

51.What is HDLC?
Ans: It is a bit oriented data link protocol designed to support both half duplex and full duplex communication over point to point and multi point links.HDLC is characterized by their station type,configuration and their response modes.

52.What do you mean by point to point protocol?
Ans: The point to point protocol was designed to provide a dedicated line for users who need internet access via a telephone line or a cable TV connection. Its connection goes through three phases: idle, establishing, authenticating, networking and terminating. At data link layer it employs a version of HDLC.

53. What do you mean by point to point protocol stack?
Ans: Point to point protocol uses a stack of other protocol to use the link, to authenticate the parties involved, and to carry the network layer data. Three sets of protocols are defined: link control protocol, Authentication protocol, and network control protocol.

54.What do you mean by line control protocol?
Ans: It is responsible for establishing, maintaining, configuring, and terminating links.

55.What do you mean by Authentication protocol?
Ans: Authentication means validating the identity of a user who needs to access a set of resources. It is of two types i)Password Authentication Protocol(PAP) ii)Challenge Handshake Authentication Protocol(CHAP) PAP is a two step process. The user sends a authentication identification and a password. The system determines the validity of the Information sent.CHAP is a three step process. The system sends a value to the user. The user manipulates the value and sends the result. The system Verifies the result.

56.What do you mean by network control protocol?
Ans: Network control protocol is a set of protocols to allow the encapsulation of data coming from network layer protocol that requires the services of PPP.

57. What do you mean by CSMA?
Ans: To reduce the possibility of collision CSMA method was developed. In CSMA each station first listen to the medium (Or check the state of the medium) before sending. It can’t eliminate collision.

58.What do you mean by Bluetooth?
Ans: It is a wireless LAN technology designed to connect devices of different functions such as telephones, notebooks, computers, cameras, printers and so on. Bluetooth LAN Is an adhoc network that is the network is formed spontaneously? It is the implementation of protocol defined by the IEEE 802.15 standard.

59.What is IP address?
Ans: The internet address (IP address) is 32bits that uniquely and universally defines a host or router on the internet. The portion of the IP address that identifies the network is called netid. The portion of the IP address that identifies the host or router on the network is called hostid.

60.What do you mean by subnetting?
Ans: Subnetting divides one large network into several smaller ones. It adds an intermediate level of hierarchy in IP addressing.

61.What are the advantages of fiber optics cable ?
Ans: The advantages of fiber optics cable over twisted pair cable are Noise resistance-As they use light so external noise is not a factor. Less signal attenuation-fiber optics transmission distance is significantly greater than that of other guided media.Higher bandwidth-It can support higher bandwidth.

62.What are the disadvantages of fiber optics cable?
Ans: The disadvantages of fiber optics cable over twisted pair cable are Cost-It is expensive Installation/maintenance-Any roughness or cracking defuses light and alters the signal Fragility-It is more fragile.

63.What are the propagation type of radio wave ?
Ans: Radio wave propagation is dependent upon frequency.There are five propagation type. i)surface propagation ii)Tropospheric propagation iii)Ionospheric propagation iv)Line of sight propagation v)space propagation

64.What do you mean by Geosynchronous Satellites ?
Ans: Satellite communication uses a satellite in geosynchronous orbit to relay signals.The Satellite must move at the same speed as the earth so that it seems to remain fixed above a certain spot..Only one orbit can be geosynchronous.This orbit occurs at the equatorial plane and is approximately 22,000 miles from the surface of earth.

65.What are the factors for evaluating the suitability of the media ?
Ans: The factors are cost,throughput,attenuation,Electromagneric interference(EMI),securtty.

66.What do you mean by medium access control(MAC) sublayer.
Ans: The protocols used to determine who goes next on a multi-access channel belong to a sublayer of the data link layer is called the multi-access channel(MAC) sublayer.It is the buttom part of data link layer.

67.What do you mean by ALOHA ?
Ans: It is the method used to solve the channel allocation problem .It is used for: i)ground based radio broadcasting ii)In a network in which uncoordinated users are competing for the use of single channel. It is of two types: 1.Pure aloha 2.Slotted aloha

68.What is pure ALOHA?
Ans: It lets users transmit whenever they have data to sent.Collision may occur but due to feedback property sender can know the status of message.conflict occur when at one time more bits are transmitted.The assumptions are : i)all frame size is same for all user. ii)collision occur when frames are transmitted simultaneously iii)indefinite population of no of user. iv)N=number of frames/frame time iv)it obeys poisson’s distribution if N>1 there will be collision 0<1

69.What is slotted ALOHA?
Ans: In this method time is divided into discrete intervals, each interval corresponding to one frame. It requires user to agree on slot boundaries. Here data is not send at any time instead it wait for beginning of the next slot. Thus pure ALOHA is tuened into discrete one.

70.What do you mean by persistent CSMA(carrier sense multiple access) ?
Ans: When a station has data to send, it first listens to the channel to see if anyone else is transmitting at that moment. If channel is busy it waits until the station becomes idle. When collision occurs it waits and then sends. It sends frame with probability 1 when channel is idle.

71.What do you mean by non persistent CSMA(carrier sense multiple access) ?
Ans: Here if no one else is sending the station begins doing so itself.However if the channel is already in use,the station does’t continuously sense it rather it waits for a random period of time and then repeats.It leads better channel utilization but longer delay.

72.What do you mean by p persistent CSMA(carrier sense multiple access) ?
Ans: It applies to slotted channels.when a station becomes ready to send,it senses the channel.If it is idle it transmits with a probability P,with a probability Q=P-1 It defers until the next slot.If that slot is also idle,it either transmits or defers again with probability P and Q.The process is repeated until either the frame has been transmitted or another station begins transmitting.

73.What is FDDI?
Ans: It is high performance fiber optic token ring LAN running at 100Mbps over distance up 1000 stations.FDDI access is limited by time.A FDDI cabling consist of two fiber rings. i)one transmitting clockwise ii)one transmitting counterclockwise

74.What is Firewalls?
Ans: It is an electronic downbridge which is used to enhance the security of a network. It’s configuration has two components. i)Two routers ii)Application gateway the packets traveling through the LAN are inspected here and packets meeting certain criteria are forwarded and others are dropped.

75.What is Repeaters ?
Ans: A receiver receives a signal before it becomes too weak or corrupted,regenerates the original bit pattern,and puts the refreshed copy back onto the link.It operates on phycal layer of OSI model.

76.What is Bridges?
Ans: They divide large network into smaller components.They can relay frames between two originally separated LANs.They provide security through partitioning traffic.They operate on phycal and data link layer of OSI model.

77.What is Routers ?
Ans: Router relay packets among multiple interconnected networks.They receive packet from one connected network and pass it to another network.They have access to network layer addresses and certain software that enables them to determine which path is best for transmission among several paths.They operate on phycal,data link and network layer of OSI model.

78.What is Gateway ?
Ans: It is a protocol converter.A gateway can accept a packet formatted for one protocol and convert it to a packet formatted for another protocol.It operates on all the seven layers of OSI model.

79.What do you mean by Data Terminal Equipment(DTE) ?
Ans: It is any device that is source of or destination for binary digital data.At phycal layer it can be a terminal computer. They generate or consume information.

80.What do you mean by Data Terminating Equipment (DCE) ?
Ans: Data circuit terminating equipment includes any functional unit that transmit or receives data in the form of an analog or digital signal through a network.DTE generates digital data and passes them to a DCE ,the DCE converts the data to a form acceptable to the transmission media and sends the converted signal to another DCE on the network.

81.What do you mean by protocol stack ?
Ans: The list of protocols used by certain system ,one protocol per layer is called protocol stack.

82.What do you mean by peer ?
Ans: Entities comprising the corresponding layers on different machines are called peers.It may be • hardware device. • processes • human being peers communicate by using protocol.

83.What do you mean by broadcasting ?
Ans: Broadcast system allow addressing a packet to all destination by using a special code in address field.when packet is transmitted it is received and processed by every machine on the network.

84.What are the advantages of broadcast network.
Ans: • a single communication channel is shared by all computers. • packets are transmitted and received by all the computer. • address field is attached to whom it is intended. • multicasting is used in network.

85.What do you mean by point to point network?
Ans: Point to point network consist of many connections between individual pair of machines.large networks are point to point.Routing algorithm plays an important in point to point network.It uses stored ad forword technique.It is a packet switching network.

86.What are the design issue of layers ?
Ans: The design issue of layer are • Addressing technique.ie source and destination address • Types of communication • Error control • Order of message. • Speed matching • Multiplexing and demultiplexing.

87.What are the protocols in application layer ?
Ans: The protocols defined in application layer are • TELNET • FTP • SMTP • DNS

88.What are the protocols in transport layer ?
Ans: The protocols defined in transport layer are
• TCP • UDP

89.Define TCP ?
Ans: It is connection oriented protocol.It consist byte streams oeiginating on one machine to be delivered without error on any other machine in the network.while transmitting it fragments the stream to discrete messages and passes to interner layer.At the destination it reassembles the messages into output stream.

90.Define UDP ?
Ans: It is unreliable connectionless protocol.It is used for one-shot,client-server type,requesr-reply queries and applications in which prompt delivery is required than accuracy.

91.Define IP ?
Ans: Internetwork protocol (IP) is the transmission mechanism used by TCP/IP protocol.It is an unreliable and connectionless datagram protocol.It provides no error checking and tracking.

92.What do you mean by client server model ?
Ans: In client server model ,the client runs a program to request a service and the server runs a program to provide the service.These two programs communicate with each other. One server program can provide services to many client programs.

93.What are the information that a computer attached to a TCP/IP internet must possesses ?
Ans: Each computer attached to TCP/IP must possesses the following information • Its IP addesss • Its subnet mask • The IP addesss of the router. • The Ip address of the name server.

94.What is domain name system(DNS)?
Ans: Domain Name System (DNS )is a client server application that identifies each host on the internet with a unique user friendly name.

95.What is TELNET ?
Ans: TELNET is a client –server application that allows a user to log on to a remote machine,giving the user access to the remote system. TELNET is an abbreviation of terminal Network.

96.What do you mean by local login and remote login ?
Ans: When a user logs into a local time-sharing system ,it is called local login. When a user wants to access an application program or utility located on a remote machine,he or she performs remote login.

97.What is Network Virtual Terminal ?
Ans: A universal interface provided by TELNET is called Network Virtual Terminal(NVT) character set.Via this interface TELNET translates characters (data or command) that come from local terminal into NVT form and delivers them to the network.

98.What do you mean by Simple Mail Transfer Protocol ?
Ans: The TCP/IP protocol that supports electronic mail on the internet is called Simple Mail Transfer Protocol.SMTP provides for mail exchange between users on the same or different computer and supports Sending a single message to one or more recipient Sending message that include text, voice,video,or graphics.Sending message to users on network outside the internet.

99.What is Hypertext Transfer Protocol(HTTP) ?
Ans: It is the main protocol used to access data on the World Wide Web .the protol transfers data in the form of plain text,hypertext,audio,video,and so on. It is so called because its efficiency allows its use in a hypertext environment where there are rapid jumps from one document to another.

100.What is URL ?
Ans: It is a standard for specifying any kind of information on the World Wide Web.

101. What is World Wide Web ?
Ans: World Wide Web is a repository of information spread all over the world and linked together.It is a unique combination of flexibility,portability,and user-friendly features .The World Wide Web today is a distributed client-server service,in which a client using a browser can access a service using a server.The service provided is distributed over many locations called web sites.

102.What is HTML ?
Ans: Hypertext Markup Language (HTML) is a language for creating static web pages

1.What is an operating system?
Ans: An operating system is a program that acts as an intermediary between the user and the computer hardware. The purpose of an OS is to provide a convenient environment in which user can execute programs in a convenient and efficient manner.It is a resource allocator responsible for allocating system resources and a control program which controls the operation of the computer h/w.

2.What are the various components of a computer system?
Ans: 1. The hardware 2. The operating system 3. The application programs 4. The users.

3.What is purpose of different operating systems?
Ans:The machine Purpose Workstation individual usability &Resources utilization Mainframe Optimize utilization of hardware PC Support complex games, business application Hand held PCs Easy interface & min. power consumption

4.What are the different operating systems?
Ans: 1. Batched operating systems 2. Multi-programmed operating systems 3. timesharing operating systems 4. Distributed operating systems 5. Real-time operating systems

6.What is a boot-strap program?

7.What is BIOS?

8.Explain the concept of the batched operating systems?
Ans: In batched operating system the users gives their jobs to the operator who sorts the programs according to their requirements and executes them. This is time consuming but makes the CPU busy all the time.

9.Explain the concept of the multi-programmed operating systems?
Ans: A multi-programmed operating systems can execute a number of programs concurrently. The operating system fetches a group of programs from the job-pool in the secondary storage which contains all the programs to be executed, and places them in the main memory. This process is called job scheduling. Then it chooses a program from the ready queue and gives them to CPU to execute. When a executing program needs
some I/O operation then the operating system fetches another program and hands it to the CPU for execution, thus keeping the CPU busy all the time.

10.Explain the concept of the timesharing operating systems?
Ans: It is a logical extension of the multi-programmed OS where user can interact with the program. The CPU executes multiple jobs by switching among them, but the switches occur so frequently that the user feels as if the operating system is running only his program.

11.Explain the concept of the multi-processor systems or parallel systems?
Ans: They contain a no. of processors to increase the speed of execution, and reliability, and economy. They are of two types: 1. Symmetric multiprocessing 2. Asymmetric multiprocessing In Symmetric multi processing each processor run an identical copy of the OS, and these copies communicate with each other as and when needed.But in Asymmetric multiprocessing each processor is assigned a specific task.

12.Explain the concept of the Distributed systems?
Ans: Distributed systems work in a network. They can share the network resources,communicate with each other

13.Explain the concept of Real-time operating systems?
Ans: A real time operating system is used when rigid time requirement have been placed on the operation of a processor or the flow of the data; thus, it is often used as a control device in a dedicated application. Here the sensors bring data to the computer. The computer must analyze the data and possibly adjust controls to modify the sensor input. They are of two types: 1. Hard real time OS 2. Soft real time OS Hard-real-time OS has well-defined fixed time constraints. But soft real time operating systems have less stringent timing constraints.

14.Define MULTICS?
Ans: MULTICS (Multiplexed information and computing services) operating system was developed from 1965-1970 at Massachusetts institute of technology as a computing utility. Many of the ideas used in MULTICS were subsequently used in UNIX.

15.What is SCSI?
Ans: Small computer systems interface.

16.What is a sector?
Ans: Smallest addressable portion of a disk.

17.What is cache-coherency?
Ans: In a multiprocessor system there exist several caches each may containing a copy of same variable A. Then a change in one cache should immediately be reflected in all other caches this process of maintaining the same value of a data in all the caches s called cache-coherency.

18.What are residence monitors?
Ans: Early operating systems were called residence monitors.

19.What is dual-mode operation?
Ans: In order to protect the operating systems and the system programs from the malfunctioning programs the two mode operations were evolved: 1. System mode. 2. User mode. Here the user programs cannot directly interact with the system resources, instead they request the operating system which checks the request and does the required task for the user programs-DOS was written for / intel 8088 and has no dual-mode. Pentium provides dual-mode operation.

20.What are the operating system components?
Ans: 1. Process management 2. Main memory management 3. File management 4. I/O system management 5. Secondary storage management 6. Networking 7. Protection system 8. Command interpreter system

21.What are operating system services?
Ans: 1. Program execution 2. I/O operations 3. File system manipulation 4. Communication 5. Error detection 6. Resource allocation 7. Accounting 8. Protection

22.What are system calls?
Ans: System calls provide the interface between a process and the operating system. System calls for modern Microsoft windows platforms are part of the win32 API, which is available for all the compilers written for Microsoft windows.

23.What is a layered approach and what is its advantage?
Ans: Layered approach is a step towards modularizing of the system, in which the operating system is broken up into a number of layers (or levels), each built on top of lower layer. The bottom layer is the hard ware and the top most is the user interface.The main advantage of the layered approach is modularity. The layers are selected such that each uses the functions (operations) and services of only lower layer. This approach simplifies the debugging and system verification.

24.What is micro kernel approach and site its advantages?
Ans: Micro kernel approach is a step towards modularizing the operating system where all nonessential components from the kernel are removed and implemented as system and user level program, making the kernel smaller.The benefits of the micro kernel approach include the ease of extending the operating system. All new services are added to the user space and consequently do not require modification of the kernel. And as kernel is smaller it is easier to upgrade it. Also this approach provides more security and reliability since most services are running as user processes rather than kernel’s keeping the kernel intact.

25.What are a virtual machines and site their advantages?
Ans: It is the concept by which an operating system can create an illusion that a process has its own processor with its own (virtual) memory. The operating system implements virtual machine concept by using CPU scheduling and virtual memory.
1. The basic advantage is it provides robust level of security as each virtual machine is isolated from all other VM. Hence the system resources are completely protected. 2. Another advantage is that system development can be done without disrupting normal operation. System programmers are given their own virtual machine, and as system development is done on the virtual machine instead of on the actual physical machine. 3. Another advantage of the virtual machine is it solves the compatibility problem. EX: Java supplied by Sun micro system provides a specification for java virtual machine.

26.What is a process?
Ans: A program in execution is called a process. Or it may also be called a unit of work. A process needs some system resources as CPU time, memory, files, and i/o devices to accomplish the task. Each process is represented in the operating system by a process control block or task control block (PCB).Processes are of two types: 1. Operating system processes 2. User processes

27.What are the states of a process?
Ans: 1. New 2. Running 3. Waiting 4. Ready 5. Terminated

28.What are various scheduling queues?
Ans: 1. Job queue 2. Ready queue 3. Device queue

29.What is a job queue?
Ans: When a process enters the system it is placed in the job queue.

30.What is a ready queue?
Ans: The processes that are residing in the main memory and are ready and waiting to execute are kept on a list called the ready queue.

31.What is a device queue?
Ans: A list of processes waiting for a particular I/O device is called device queue.

32.What is a long term scheduler & short term schedulers?
Ans: Long term schedulers are the job schedulers that select processes from the job queue and load them into memory for execution. The short term schedulers are the CPU schedulers that select a process form the ready queue and allocate the CPU to one of them.

33.What is context switching?
Ans: Transferring the control from one process to other process requires saving the state of the old process and loading the saved state for new process. This task is known as context switching.

34.What are the disadvantages of context switching?
Ans: Time taken for switching from one process to other is pure over head. Because the system does no useful work while switching. So one of the solutions is to go for threading when ever possible.

35.What are co-operating processes?
Ans: The processes which share system resources as data among each other. Also the processes can communicate with each other via interprocess communication facility generally used in distributed systems. The best example is chat program used on the www.

36.What is a thread?
Ans: A thread is a program line under execution. Thread sometimes called a light-weight process, is a basic unit of CPU utilization; it comprises a thread id, a program counter, a register set, and a stack.

37.What are the benefits of multithreaded programming?
Ans: 1. Responsiveness (needn’t to wait for a lengthy process)
2. Resources sharing 3. Economy (Context switching between threads is easy) 4. Utilization of multiprocessor architectures (perfect utilization of the multiple processors).

38.What are types of threads?
Ans: 1. User thread 2. Kernel thread User threads are easy to create and use but the disadvantage is that if they perform a blocking system calls the kernel is engaged completely to the single user thread blocking other processes. They are created in user space.Kernel threads are supported directly by the operating system. They are slower to create and manage. Most of the OS like Windows NT, Windows 2000, Solaris2, BeOS, and Tru64 Unix support kernel threading.

39.Which category the java thread do fall in?
Ans: Java threads are created and managed by the java virtual machine, they do not easily fall under the category of either user or kernel thread……

40.What are multithreading models?
Ans: Many OS provide both kernel threading and user threading. They are called multithreading models. They are of three types: 1. Many-to-one model (many user level thread and one kernel thread). 2. One-to-one model 3. Many-to –many In the first model only one user can access the kernel thread by not allowing multi-processing. Example: Green threads of Solaris.The second model allows multiple threads to run on parallel processing systems. Creating user thread needs to create corresponding kernel thread (disadvantage).Example: Windows NT, Windows 2000, OS/2.The third model allows the user to create as many threads as necessary and the corresponding kernel threads can run in parallel on a multiprocessor. Example: Solaris2, IRIX, HP-UX, and Tru64 Unix.

41.What is a P-thread?
Ans: P-thread refers to the POSIX standard (IEEE 1003.1c) defining an API for thread creation and synchronization. This is a specification for thread behavior, not an implementation. The windows OS have generally not supported the P-threads.

42.What are java threads?
Ans: Java is one of the small number of languages that support at the language level for the creation and management of threads. However, because threads are managed by the java virtual machine (JVM), not by a user-level library or kernel, it is difficult to classify Java threads as either user- or kernel-level.

43.What is process synchronization?
Ans: A situation, where several processes access and manipulate the same data concurrently and the outcome of the execution depends on the particular order in which the access takes place, is called race
condition. To guard against the race condition we need to ensure that only one process at a time can be manipulating the same data. The technique we use for this is called process synchronization.

44.What is critical section problem?
Ans: Critical section is the code segment of a process in which the process may be changing common variables, updating tables, writing a file and so on. Only one process is allowed to go into critical section at any given time (mutually exclusive).The critical section problem is to design a protocol that the processes can use to co-operate. The three basic requirements of critical section are: 1. Mutual exclusion 2. Progress 3. bounded waiting Bakery algorithm is one of the solutions to CS problem.

45.What is a semaphore?
Ans: It is a synchronization tool used to solve complex critical section problems. A semaphore is an integer variable that, apart from initialization, is accessed only through two standard atomic operations: Wait and Signal.

46.What is bounded-buffer problem?
Ans: Here we assume that a pool consists of n buffers, each capable of holding one item. The semaphore provides mutual exclusion for accesses to the buffer pool and is initialized to the value 1.The empty and full semaphores count the number of empty and full buffers, respectively. Empty is initialized to n, and full is initialized to 0.

47.What is readers-writers problem?
Ans: Here we divide the processes into two types: 1. Readers (Who want to retrieve the data only) 2. Writers (Who want to retrieve as well as manipulate) We can provide permission to a number of readers to read same data at same time.But a writer must be exclusively allowed to access. There are two solutions to this problem: 1. No reader will be kept waiting unless a writer has already obtained permission to use the shared object. In other words, no reader should wait for other readers to complete simply because a writer is waiting. 2. Once a writer is ready, that writer performs its write as soon as possible. In other words, if a writer is waiting to access the object, no new may start reading.

48.What is dining philosophers’ problem?
Ans: Consider 5 philosophers who spend their lives thinking and eating. The philosophers share a common circular table surrounded by 5 chairs, each belonging to one philosopher. In the center of the table is a bowl of rice, and the table is laid with five single chop sticks. When a philosopher thinks, she doesn’t interact with her colleagues.
From time to time, a philosopher gets hungry and tries to pick up two chop sticks that are closest to her .A philosopher may pick up only one chop stick at a time. Obviously she can’t pick the stick in some others hand. When a hungry philosopher has both her chopsticks at the same time, she eats without releasing her chopsticks. When she is finished eating, she puts down both of her chopsticks and start thinking again.

49.What is a deadlock?
Ans: Suppose a process request resources; if the resources are not available at that time the process enters into a wait state. A waiting process may never again change state, because the resources they have requested are held by some other waiting processes. This situation is called deadlock.

50.What are necessary conditions for dead lock?
Ans: 1. Mutual exclusion (where at least one resource is non-sharable) 2. Hold and wait (where a process hold one resource and waits for other resource) 3. No preemption (where the resources can’t be preempted) 4. circular wait (where p[i] is waiting for p[j] to release a resource. i= 1,2,…n j=if (i!=n) then i+1 else 1 )

51.What is resource allocation graph?
Ans: This is the graphical description of deadlocks. This graph consists of a set of edges E and a set of vertices V. The set of vertices V is partitioned into two different types of nodes P={p1,p2,…,pn}, the set consisting of all the resources in the system, R={r1,r2,…rn}.A directed edge Pi?Rj is called a request edge; a directed edge Rj? Pi is called an assignment edge. Pictorially we represent a process Pi as a circle, and each resource type Rj as square.Since resource type Rj may have more than one instance, we represent each such instance as a dot within the square.When a request is fulfilled the request edge is transformed into an assignment edge. When a process releases a resource the assignment edge is deleted. If the cycle involves a set of resource types, each of which has only a single instance, then a deadlock has occurred. Each process involved in the cycle is deadlock.

52.What are deadlock prevention techniques?
Ans: 1. Mutual exclusion : Some resources such as read only files shouldn’t be mutually exclusive. They should be sharable. But some resources such as printers must be mutually exclusive. 2. Hold and wait : To avoid this condition we have to ensure that if a process is requesting for a resource it should not hold any resources. 3. No preemption : If a process is holding some resources and requests another resource that cannot be immediately allocated to it (that is the process must wait), then all the resources currently being held are preempted(released autonomously). 4. Circular wait : the way to ensure that this condition never holds is to impose a
total ordering of all the resource types, and to require that each process requests resources in an increasing order of enumeration.

53.What is a safe state and a safe sequence?
Ans: A system is in safe state only if there exists a safe sequence. A sequence of processes is a safe sequence for the current allocation state if, for each Pi, the resources that the Pi can still request can be satisfied by the currently available resources plus the resources held by all the Pj, with j

54.What are the deadlock avoidance algorithms?
Ans: A dead lock avoidance algorithm dynamically examines the resource-allocation state to ensure that a circular wait condition can never exist. The resource allocation state is defined by the number of available and allocated resources, and the maximum demand of the process.There are two algorithms: 1. Resource allocation graph algorithm 2. Banker’s algorithm a. Safety algorithm b. Resource request algorithm

55. What are the basic functions of an operating system?
Ans : Operating system controls and coordinates the use of the hardware among the various applications programs for various uses. Operating system acts as resource allocator and manager. Since there are many possibly conflicting requests for resources the operating system must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls the user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.

56.Explain briefly about, processor, assembler, compiler, loader, linker and the functions executed by them.
Ans : Processor:–A processor is the part a computer system that executes instructions .It is also called a CPU Assembler: — An assembler is a program that takes basic computer instructions and converts them into a pattern of bits that the computer’s processor can use to perform its basic operations. Some people call these instructions assembler language and others use the term assembly language. Compiler: — A compiler is a special program that processes statements written in a particular programming language and turns them into machine language or “code” that a computer’s processor uses. Typically, a programmer writes language statements in a language such as Pascal or C one line at a time using an editor. The file that is created contains what are called the source statements. The programmer then runs the appropriate language compiler, specifying the name of the file that contains the source statements. Loader:–In a computer operating system, a loader is a component that locates a given program (which can be an application or, in some cases, part of the operating system itself) in offline storage (such as a hard disk), loads it into main storage (in a personal computer, it’s called random access memory), and gives that program control of the compute
Linker: — Linker performs the linking of libraries with the object code to make the object code into an executable machine code.

57. What is a Real-Time System?
Ans : A real time process is a process that must respond to the events within a certain time period. A real time operating system is an operating system that can run real time processes successfully

58. What is the difference between Hard and Soft real-time systems?
Ans : A hard real-time system guarantees that critical tasks complete on time. This goal requires that all delays in the system be bounded from the retrieval of the stored data to the time that it takes the operating system to finish any request made of it. A soft real time system where a critical real-time task gets priority over other tasks and retains that priority until it completes. As in hard real time systems kernel delays need to be bounded

59. What is virtual memory?
Ans : A virtual memory is hardware technique where the system appears to have more memory that it actually does. This is done by time-sharing, the physical memory and storage parts of the memory one disk when they are not actively being used

60. What is cache memory?
Ans : Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data

61.Differentiate between Complier and Interpreter?
Ans : An interpreter reads one instruction at a time and carries out the actions implied by that instruction. It does not perform any translation. But a compiler translates the entire instructions.

62.What are different tasks of Lexical Analysis?
Ans : The purpose of the lexical analyzer is to partition the input text, delivering a sequence of comments and basic symbols. Comments are character sequences to be ignored, while basic symbols are character sequences that correspond to terminal symbols of the grammar defining the phrase structure of the input

63. Why paging is used?
Ans : Paging is solution to external fragmentation problem which is to permit the logical address space of a process to be noncontiguous, thus allowing a process to be allocating physical memory wherever the latter is available.

64. What is Context Switch?
Ans : Switching the CPU to another process requires saving the state of the old process and loading the saved state for the new process. This task is known as a context switch.Context-switch time is pure overhead, because the system does no useful work while switching. Its speed varies from machine to
machine, depending on the memory speed, the number of registers which must be copied, the existed of special instructions(such as a single instruction to load or store all registers).

65. Distributed Systems?
Ans : Distribute the computation among several physical processors. Loosely coupled system – each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines Advantages of distributed systems: ->Resources Sharing ->Computation speed up – load sharing ->Reliability ->Communications

66.Difference between Primary storage and secondary storage?
Ans : Main memory: – only large storage media that the CPU can access directly. Secondary storage: – extension of main memory that provides large nonvolatile storage capacity.

67. What is CPU Scheduler?
Ans : ->Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. ->CPU scheduling decisions may take place when a process: 1.Switches from running to waiting state. 2.Switches from running to ready state. 3.Switches from waiting to ready. 4.Terminates. ->Scheduling under 1 and 4 is nonpreemptive. ->All other scheduling is preemptive.

68. What do you mean by deadlock?
Ans : Deadlock is a situation where a group of processes are all blocked and none of them can become unblocked until one of the other becomes unblocked.The simplest deadlock is two processes each of which is waiting for a message from the other

69. What is Dispatcher?
Ans : ->Dispatcher module gives control of the CPU to the process selected by the short-term scheduler; this involves: Switching context Switching to user mode Jumping to the proper location in the user program to restart that program Dispatch latency – time it takes for the dispatcher to stop one process and start another running.

70. What is Throughput, Turnaround time, waiting time and Response time?
Ans : Throughput – number of processes that complete their execution per time unit Turnaround time – amount of time to execute a particular process Waiting time – amount of time a process has been waiting in the ready queue Response time – amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment)

71. Explain the difference between microkernel and macro kernel?
Ans :Micro-Kernel: A micro-kernel is a minimal operating system that performs only the essential functions of an operating system. All other operating system functions are performed by system processes. Monolithic: A monolithic operating system is one where all operating system code is in a single executable image and all operating system code runs in system mode.

72.What is multi tasking, multi programming, multi threading?
Ans : Multi programming: Multiprogramming is the technique of running several programs at a time using timesharing.It allows a computer to do several things at the same time. Multiprogramming creates logical parallelism. The concept of multiprogramming is that the operating system keeps several jobs in memory simultaneously. The operating system selects a job from the job pool and starts executing a job, when that job needs to wait for any i/o operations the CPU is switched to another job. So the main idea here is that the CPU is never idle. Multi tasking: Multitasking is the logical extension of multiprogramming .The concept of multitasking is quite similar to multiprogramming but difference is that the switching between jobs occurs so frequently that the users can interact with each program while it is running. This concept is also known as time-sharing systems. A time-shared operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of time-shared system. Multi threading: An application typically is implemented as a separate process with several threads of control. In some situations a single application may be required to perform several similar tasks for example a web server accepts client requests for web pages, images, sound, and so forth. A busy web server may have several of clients concurrently accessing it. If the web server ran as a traditional single-threaded process, it would be able to service only one client at a time. The amount of time that a client might have to wait for its request to be serviced could be enormous. So it is efficient to have one process that contains multiple threads to serve the same purpose. This approach would multithread the web-server process, the server would create a separate thread that would listen for client requests when a request was made rather than creating another process it would create another thread to service the request. So to get the advantages like responsiveness, Resource sharing economy and utilization of multiprocessor architectures multithreading concept can be used

73. Give a non-computer example of preemptive and non-preemptive scheduling?
Ans : Consider any system where people use some kind of resources and compete for them. The non-computer examples for preemptive scheduling the traffic on the single lane road if there is emergency or there is an ambulance on the road the other vehicles give path to the vehicles that are in need. The example for preemptive scheduling is people standing in queue for tickets.

74. What is starvation and aging?
Ans : Starvation: Starvation is a resource management
problem where a process does not get the resources it needs for a long time because the resources are being allocated to other processes. Aging: Aging is a technique to avoid starvation in a scheduling system. It works by adding an aging factor to the priority of each request. The aging factor must increase the request’s priority as time passes and must ensure that a request will eventually be the highest priority request (after it has waited long enough)

75.Different types of Real-Time Scheduling?
Ans :Hard real-time systems – required to complete a critical task within a guaranteed amount of time. Soft real-time computing – requires that critical processes receive priority over less fortunate ones.

76. What are the Methods for Handling Deadlocks?
Ans : ->Ensure that the system will never enter a deadlock state. ->Allow the system to enter a deadlock state and then recover. ->Ignore the problem and pretend that deadlocks never occur in the system; used by most operating systems, including UNIX.

77. What is a Safe State and its’ use in deadlock avoidance?
Ans :When a process requests an available resource, system must decide if immediate allocation leaves the system in a safe state ->System is in safe state if there exists a safe sequence of all processes. ->Sequence is safe if for each Pi, the resources that Pi can still request can be satisfied by currently available resources + resources held by all the Pj, with j If Pi resource needs are not immediately available, then Pi can wait until all Pj have finished. When Pj is finished, Pi can obtain needed resources, execute, return allocated resources, and terminate. When Pi terminates, Pi+1 can obtain its needed resources, and so on. ->Deadlock Avoidance Þ ensure that a system will never enter an unsafe state.

78. Recovery from Deadlock?
Ans :Process Termination: ->Abort all deadlocked processes. ->Abort one process at a time until the deadlock cycle is eliminated. ->In which order should we choose to abort?
Priority of the process. How long process has computed, and how much longer to completion. Resources the process has used. Resources process needs to complete. How many processes will need to be terminated? Is process interactive or batch? Resource Preemption: ->Selecting a victim – minimize cost. ->Rollback – return to some safe state, restart process for that state. ->Starvation – same process may always be picked as victim, include number of rollback in cost factor.

79.Difference between Logical and Physical Address Space?
Ans : ->The concept of a logical address space that is bound to a separate physical address space is central to proper memory management. Logical address – generated by the CPU; also referred to as virtual address. Physical address – address seen by the memory unit. ->Logical and physical addresses are the same in compile-time and load-time address-binding schemes; logical (virtual) and physical addresses differ in execution-time address-binding scheme

80. Binding of Instructions and Data to Memory?
Ans :Address binding of instructions and data to memory addresses can happen at three different stages Compile time: If memory location known a priori, absolute code can be generated; must recompile code if starting location changes. Load time: Must generate relocatable code if memory location is not known at compile time. Execution time: Binding delayed until run time if the process can be moved during its execution from one memory segment to another. Need hardware support for address maps (e.g., base and limit registers).

81. What is Memory-Management Unit (MMU)?
Ans :Hardware device that maps virtual to physical address. In MMU scheme, the value in the relocation register is added to every address generated by a user process at the time it is sent to memory. ->The user program deals with logical addresses; it never sees the real physical addresses

82. What are Dynamic Loading, Dynamic Linking and Overlays?
Ans : Dynamic Loading: ->Routine is not loaded until it is called ->Better memory-space utilization; unused routine is never loaded. ->Useful when large amounts of code are needed to handle infrequently occurring cases. ->No special support from the operating system is required implemented through program design. Dynamic Linking:
->Linking postponed until execution time. ->Small piece of code, stub, used to locate the appropriate memory-resident library routine. ->Stub replaces itself with the address of the routine, and executes the routine. ->Operating system needed to check if routine is in processes’ memory address. ->Dynamic linking is particularly useful for libraries. Overlays: ->Keep in memory only those instructions and data that are needed at any given time. ->Needed when process is larger than amount of memory allocated to it. ->Implemented by user, no special support needed from operating system, programming design of overlay structure is complex.

83. What is fragmentation?
Different types of fragmentation? Ans : Fragmentation occurs in a dynamic memory allocation system when many of the free blocks are too small to satisfy any request. External Fragmentation: External Fragmentation happens when a dynamic memory allocation algorithm allocates some memory and a small piece is left over that cannot be effectively used. If too much external fragmentation occurs, the amount of usable memory is drastically reduced.Total memory space exists to satisfy a request, but it is not contiguous Internal Fragmentation: Internal fragmentation is the space wasted inside of allocated memory blocks because of restriction on the allowed sizes of allocated blocks.Allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used Reduce external fragmentation by compaction ->Shuffle memory contents to place all free memory together in one large block. ->Compaction is possible only if relocation is dynamic, and is done at execution time.

84. Define Demand Paging, Page fault interrupt, and Trashing?
Ans : Demand Paging: Demand paging is the paging policy that a page is not read into memory until it is requested, that is, until there is a page fault on the page. Page fault interrupt: A page fault interrupt occurs when a memory reference is made to a page that is not in memory.The present bit in the page table entry will be found to be off by the virtual memory hardware and it will signal an interrupt. Trashing: The problem of many page faults occurring in a short time, called “page thrashing,”

85. Explain Segmentation with paging?
Ans : Segments can be of different lengths, so it is harder to find a place for a segment in memory than a page. With segmented virtual memory, we get the benefits of virtual memory but we still have to do dynamic storage allocation of physical memory. In order to avoid this, it is possible to combine segmentation and paging into a two-level virtual memory system. Each segment descriptor points to page table for that segment.This give some of the advantages of paging (easy placement) with some of the advantages of segments (logical division of the program).

86. Under what circumstances do page faults occur? Describe the actions taken by the operating system when a page fault occurs?
Ans : A page fault occurs when an access to a page that has not been brought into main memory takes place. The operating system verifies the memory access, aborting the program if it is invalid. If it is valid, a free frame is located and I/O is requested to read the needed page into the free frame. Upon completion of I/O, the process table and page table are updated and the instruction is restarted

87. What is the cause of thrashing?
How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem? Ans : Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault. The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming. It can be eliminated by reducing the level of multiprogramming.