Viva Voice File( Made by Hitakshi Jain Frm Ludhiana)

8/6/2019 Viva Voice File( Made by Hitakshi Jain Frm Ludhiana)

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CHAPTER 1

INFORMATION TECHNOLOGY


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Information Technology

Define Computer

An electronic device that stores, retrieves, and processes data, and can be programmed

with instructions. A computer is composed of hardware and software, and can exist in a

variety of sizes and configurations.

Define Primary Memory

Primary storage is a category of computer storage, often called main memory.

Confusingly, the term primary storage has recently been used in a few contexts to refer to

online storage (hard disk), which is usually classified as secondary storage.

Define Secondary Memory

Secondary Storage is the non-volatile or semi-permanent storage in your computer forholding files and information until it is needed. Secondary Storage includes devices like

hard drives, floppies, CD-ROMS and tape drives. As opposed to Primary Storage which

is the volatile or temporary storage (RAM) that the CPU uses for processing data and

instructions

Operating System

The software that the rest of the software depends on to make the computer functional.

An operating system (sometimes abbreviated as "OS") is the program that, after being

initially loaded into the computer by a boot program, manages all the other programs in a

computer. The other programs are called applications or application programs. The

application programs make use of the operating system by making requests for services

through a defined application program interface (API).


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Memory Management

Memory management is the act of managing computer memory. In its simpler forms this

involves providing ways to allocate portions of memory to programs at their request andfree it back to the system for reuse when no longer needed.

Batch Processing

A type of data processing operation and data communications transmission where related

transactions are grouped together and transmitted for processing, usually by the same

computer and under the same application; generally regarded as non-real-time data traffic

consisting of large files.

Multi Processing

It refers to a computer system's ability to support more than one process (program) at the

same time. Multiprocessing operating systems enable several programs to run

concurrently. UNIX is one of the most widely used multiprocessing systems, but there

are many others, including OS/2 for high-end PCs. Multiprocessing systems are much

more complicated than single-process systems because the operating system mustallocate resources to competing processes in a reasonable manner.

Time Sharing

It refers to the concurrent use of a computer by more than one user - users share the

computer's time. Time sharing is synonymous with multi-user. Almost all mainframes

and minicomputers are time-sharing systems, but most personal computers and

workstations are not.


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Define WAN

Wide Area Network. A computer network which spans great distances. Usually connects

many LANs together. A WAN is typically used in a company or organization to connect

their sites together. Often this can be run using "Virtual Private Networks" over theInternet.

Define LAN

A LAN supplier networking capability to a group of computer in close proximity to each

other in such school and office.

Multi User

It refers to comport system that support two or more simultaneous users. All mainframes

and minicomputer are multi-user systems, but most personal computer and workstations

are not. Another term for multi-user is time sharing

Components of Information Technology

(a) Hardware

(b) Software

(c) Data

(d) User

(e) Storage

(f) Communication


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Hardware

Hardware are those tangible components of computer which one can see and feel. It

includes input and output devices, central processing unit etc.

Software

Software are set of instructions or program which are given to computer so that it works

and dose the tasks.

Data

It is collection of facts and figures, which has to be worked on by the computer.

Users

These are those people who directly or indirectly are benefited by the use of computers.

Storage

This is the component which enables the data and software components to make its place

in computer system by residing in various types of storage devices.

Communications

This is the components which enables a user to communicate with the computer as well

the computer to communicate with other computer to get various tasks done.


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Language Processors

(a)Translators

To make the computer understand it, the input has to converse into machine language.

The software which makes this conversion possible and increases the productivity of

programmer are called Translator.

There are three basic types of translators. They are:

i. Compiler

ii. Interpreters

iii. Assembler

Compiler

A complier is software that will accept total program code as input and then converts into

machine code.

Interpreter

The interpreter also does the same task of compiler. but there are some difference

between compiler and interpreter. The compiler take the complete program as input ,but

interpreter take the program code line by line and convert it in to machine code.

Assembler

It is also same as compiler and interpreter but the input was in assembly language and the

output was in machine language.


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Input / Output Devices

Input Devices

These are those devices which facilitates a user to give input, i.e. data to C.P.U to work

on. The input devices have become more and more user friendly, so that user can work

very easily without much hassle and with greater speed and accuracy.

There are many input devices these are as follow:

1. Keyboard

2. Mouse

3. Joystick

4. Trackball

5. Touch Screen6. Light Pen etc

Keyboard

The keyboard is still the commonest way of entering information into a computer. There

are a number of different types, including those specially designed for use with Microsoft

Windows. The quality of the keyboard is often overlooked when buying a PC; it should

be robust and easy to use.

Mouse

The mouse came into common use on a PC with the introduction of the MicrosoftWindows operating system. Before this, the operating system (DOS) would normally be

controlled via the keyboard.


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Joystick

Joysticks are often used to control games, and usually have one or more push-buttons

whose state can also be read by the computer. Most I/O interface cards for PCs have a

joystick (game control) port. Modern joysticks (as of 2003) mostly use a USB interfacefor connection to the PC

Trackball

A tracker ball is an alternative to the traditional mouse and favored by graphic designers.

Tracker balls often give much finer control over the movement of the items on the screen.

Touch Screen

A touch pad is a desktop device and responds to pressure. Used in conjunction with a

special pen they can be used by graphic artists wishing to create original, digital artwork.

Output Devices

Output devices can adopt different shapes and styles , which are used to give the output

of the processing data. The output can be in any form i.e. typed, printed, visible, non-

visible, audio, video etc.

1. Printer

2. Monitor

3. Visual Display Terminal

4. Plotter

Types of Printer

There are mainly two categories of printers:

A. Impact Printer

B. Non-Impact Printer


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Impact Printer

These are those types of printer which have direct mechanical contact between the headof the printer and paper.

Non-Impact Printer

These are those types of printer which have no contact between the head of the printer

and paper.

Types of Non- Impact Printer

1. Thermal Printer

2. Ink-Jet Printer3. Laser Printer

4. Electrographic Printer5. Electro Static Printer

Secondary Storage Devices

This is non volatile memory, which is external to computer. It is a secondary media used

for storing volumes of data for permanently or ling term. Virtually the size of secondary

memory is unlimited it is even much cheaper than main memory.

There are some features of the Secondary Memory:

1. Permanent or Non volatile Storage

2. Voluminous Storage

3. Relatively Cheaper4. Computing Capability

5. Portable

There are some of the commonly available categories of auxiliary storage devices:

I. Magnetic Tapes

II. Magnetic Disk

III. Optical Disks


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Magnetic Tapes

Magnetic tape has been used for data storage for over 50 years. Modern magnetic tape is

most commonly packaged in cassettes. The device that performs actual writing or reading

of data is a tape drive. When storing large amounts of data, tape can be less expensive

than disk or other data storage options. Tape storage has always been used with large

computer systems.

Advantages of Magnetic tapes

1. Large amount of data can be stored onto small lengths of magnetic tape.

2. This tape very easy to and convenient to handle.

3. This tape is very economical.4. This tape is reusable.

5. It is fast and saves time.

6. The life of magnetic tape is very high.

Disadvantages of Magnetic tapes

1. Human cannot read the data directly.

2. Searching becomes difficult.

3. It is sensitive to dust, temperature.

4. Difficult to remove from parity errors.

Magnetic Tapes

Magnetic disk is very popular means of secondary storage. Magnetic disk is usually made

up of plastic like material called mylar. All magnetic disks are round and coated with

magnetic materials.

There are two types of magnetic disks:

1. Floppy Disk

2. Hard Disk


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Advantages of Magnetic Disk

1. The magnetic disk provides easy accessibility.

2. The disk has longer life than tapes

3. We can access data both sequentially and randomly4. It is reusable.

5. We can update several online disk records by single input transactions.

Disadvantages of Magnetic Disk

1. It is bit costlier than magnetic tape.

2. Data may be lost in case when new record is written on disk.

3. Less secure.

Optical Disk

Optical disk is a compact disk or CD. The formatting of the optical disk will dictate

whether it is a DVD, CD, read-only or rewritable. Optical disks have replaced cassette

tapes, videotapes and floppy disks. The optical disk became the preferred medium for

music, movies and software programs because of its many advantages. Compact,

lightweight, durable and digital, the optical disk also provides a minimum of 650

megabytes (MB) of data storage.

Data Transmission

Data can be transmitted across the network in following two basic terms:

Analog Data Transmission

Digital Data Transmission

Analog Data Transmission

Here the data is transmitted, as a continuous wave from one terminal to another.


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Digital Data Transmission

This method of data transmission uses distinct, on and off electricity states. The

digital data transmission is fast.

Data Transmission Techniques

Data in computer system exist as digital, where as telephone lines are made to transmit

analog pulses.

1. Modulation

Before data transmission from one computer two another, the data has to beConverted from digital to analog, if telephones lines are used. This process of converting

digital data, before transmission into analog data is known as modulation.

2. Demodulation

The receiving computer has to reconvert the analog data received into digital

form, which again is done by the modem. This process of reconverting an analog signal

into digital pulses is called demodulation.

Classification of digital computer according to size and capabilities:

i. Super computer

ii. Mainframe computer

iii. Medium sized computer

iv. Mini computers

v. Micro computer

Classification of Computers

1. According to the logic used by the computer.

2. According to size of computer.


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Classification as per the logic used by Computer

i. Analog Computers

ii. Digital Computers

iii. Hybrid Computers


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CHAPTER 2

DATABASE MANAGEMNET SYSTEM


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Introduction

Database: The related information when placed in an organized form makes a Database.

OR

Database is a computer based record keeping system whose overall purpose is to record

and maintains information.

E.g. in Dictionary, words are arranged in alphabetic order along with their meanings.

A database is a collection of related information stored in a manner that it isavailable to many users for different purposes. The content of a database is obtained by

combining data from all the different sources in an organization. So that data are

available to all users and redundant data can be eliminated or at least minimized. The

DBMS helps create an environment in which end user have better access to more and

better managed data than they did before the DBMS become the data management

standard.

A database can handle business inventory, accounting information in its files to

prepare summaries, estimates, and other reports.

Advantages and Disadvantages of DBMS:

Database system is that the organization can exert, via the DBA, centralized management

and control over the data. The database administrator is the focus of the centralized

control. Any application requiring a change in the structure of a data record requires an

arrangement with the DBA, who makes the necessary modifications. Such modifications

do not affect other applications or users of The record in question. Therefore, these

changes meet another requirement of the DBMS: data Independence. The following are

the important advantages of DBMS:


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Advantages:

Reduction of Redundancies: Centralized control of data by the DBA avoids unnecessary

duplication of data and effectively reduces the total amount of data storage required. It

also eliminates the extra processing necessary to trace the required data in a large mass of

data.

Another advantage of avoiding duplication is the elimination of the inconsistencies that

tend to be present in redundant data files. Any redundancies that exist in the DBMS are

controlled and the system ensures that these multiple copies are consistent.

Sharing Data: A database allows the sharing of data under its control by any number of

Application programs or users.

Data Integrity: Centralized control can also ensure that adequate checks are incorporated

in the DBMS to provide data integrity. Data integrity means that the data contained in the

database is both accurate and consistent. Therefore, data values being entered for storage

could be checked to ensure that they fall within a specified range and are of the correct

format. For example, the value for the age of an employee may be in the range of 16 and

75. Another integrity check that should be incorporated in the database is to ensure that if

there is a reference to certain object, that object must exist. In the case of an automatic

teller machine, for example, a user is not allowed to transfer funds from a nonexistent

saving account to a checking account.

Data Security: Data is of vital importance to an organization and may be confidential.

Unauthorized persons must not access such confidential data. The DBA who has the

ultimate responsibility for the data in the DBMS can ensure that proper access procedures

are followed, including proper authentication schemas for access to the DBMS and

additional checks before permitting access to sensitive data. Different levels of security

could be implemented for various types of data and operations.

Conflict Resolution: DBA chooses the best file structure and access method to get

optimal Performance for the response-critical applications, while permitting less critical

applications to continue to use die database, albeit with a relatively slower response.

Data Independence: Data independence is usually considered from two points of view:

physical data independence and logical data independence. Physical data independence

allows changes in the physical storage devices or organization of the files to be made


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without requiring changes in the conceptual view or any of the external views and hence

in the application programs using the database.

Disadvantages:

A significant disadvantage of the DBMS system is cost. In addition to the cost of

purchasing or developing the software, the hardware has to be upgraded to allow for the

extensive programs and the workspaces required for their execution and storage. The

processing overhead introduced by the DBMS to implement security, integrity, and

sharing of the data causes a degradation of the response and through-put times. An

additional cost is that of migration from a traditionally separate application environment

to an integrated one.

While centralization reduces duplication, the lack of duplication requires that the

database be adequately backed up so that in the case of failure the data can be recovered.Backup and recovery operations are fairly complex in a DBMS environment, and this is

exacerbated in a concurrent multi user database system. In further a database system

requires a certain amount of controlled redundancies and duplication to enable access to

related data items.

Centralization also means that the data is accessible from a single source namely the

database.

This increases the potential severity of security breaches and disruption of the operation

of the organization because of downtimes and failures. The replacement of a monolithic

centralized database by a federation of independent and cooperating distributed databasesresolves some of the problems resulting from failures and downtimes.


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THE THREE LEVEL ARCHITECTURE OF DBMS

A database management system that provides these three levels of data is said to follow

three level architecture as shown in fig. These three levels are the external level, theconceptual level, and the internal level.

The three level architecture for a DBMS

A schema describes the view at each of these levels. A schema as mentioned earlier is an

outline or plan that describes the records and relationships existing in the view. The

schema also describes the way in which entities at one level of abstraction can be mapped

to the next level. The overall design of the database is called the database schema. A

database schema includes such information as: Characteristics of data items such asentities and attributes Format for storage representation Integrity parameters such as

physically authorization and backup politics. Logical structure and relationship among

those data items.

In general, database system supports one physical schema, one conceptual schema, and

several sub-schemas.


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External Level or Subschema

The external level is at the highest level of database abstraction where only those portions

of the database of concern to a user or application program are included. Any number ofuser views may exist for a given global or conceptual view.

Each external view is described by means of a schema called an external schema or

subschema. The external schema consists of the, definition of the logical records and the

relationships in the external view. The external schema also contains the method of

deriving the objects in the external view from the objects in the conceptual view. The

objects include entities, attributes, and relationships.

Conceptual Level or Conceptual Schema

One conceptual view represents the entire database. The conceptual schema defines this

conceptual view. It describes all the records and relationships included in the conceptual

view and, therefore, in the database. There is only one conceptual schema per database.

This schema also contains the method of deriving the objects in the conceptual view from

the objects in the internal view. The description of data at this level is in a format

independent of its physical representation. It also includes features that specify the checks

to retain data consistency and integrity.

Internal Level or Physical Schema

It indicates how the data will be stored and describes the data structures and accessmethods to be used by the database. The internal schema, which contains the definition of

the stored record, the method of representing the data fields, expresses the internal view

and the access aids used.

Mapping between different Levels

Two mappings are required in a database system with three different views. A mapping

between the external and conceptual level gives the correspondence among the records

and the relationships of the external and conceptual levels.

a) EXTERNAL to CONCEPTUAL: Determine how the conceptual record is viewed bythe user

b) INTERNAL to CONCEPTUAL: Enable correspondence between conceptual and

internal levels. It represents how the conceptual record is represented in storage.


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External/Conceptual Mapping:

It gives the correspondence among the records and the relationships of the external and

conceptual views.

External view is an abstraction of the conceptual view, which in turn is an abstraction of

the internal view.

It describes the contents of the database as perceived by the user or application program

of that view.

For e.g. Names of the fields and records, for instance may be different. A no. of

conceptual fields can be combined into a single external field, like Last_Name and

First_Name at the conceptual level but Name at the external level.

Conceptual/Internal Mapping

It enables the DBMS to find the actual records or combination of records in physicalstorage that constitute an logical record in conceptual schema.

Mapping between the conceptual and the internal levels specifies the method of deriving

the conceptual record from the physical database.

Data Independence: it means that upper levels are unaffected by changes in the lower

level.

Types of Data Independence

o Logical Data Independence

o Physical Data Independence

Logical Data Independence: It indicates that the conceptual schema can be changed

without affecting the existing external schema.

For e.g. Names of the fields and records, for instance may be different. A no. of

conceptual fields can be combined into a single external field, like Last_Name and

First_Name at the conceptual level but Name at the external level. Now if the First and

Last name is joined in Conceptual level it will not result in any change in External level.

Physical Data Independence: It indicates that the physical storage structures or devices

could be changed without affecting conceptual schema.

For e.g. If there is a need to change the file organization or the type of physical

device used as a result of growth in the database or new technology, a change is


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required in the conceptual/internal mapping between the conceptual and internal

levels.

ENTITY-RELATIONSHIP (E-R) DIAGRAM

The entity-relationship model is a tool for analyzing the semantic features of an

application that are independent of events. Entity-relationship modeling helps reduce data

redundancy. This approach includes a graphical notation which depicts entity classes as

rectangles, relationships as diamonds, and attributes as circles or ovals. For complex

situations a partial entity-relationship diagram may be used to present a summary of the

entities and relationships but not include the details of the attributes.

Following are short definitions of some of the basic terms that are used for describing

important entity-relationship concepts:

Entity - An entity is a thing that exists and is distinguishable -- an object, something in

the environment.

o Entity Instance - An instance is a particular occurrence of an entity. For example, each

person is an instance of an entity, each car is an instance of an entity, etc.

o Entity Set - A group of similar entities is called an entity class or entity class or entity

type. An Entity Class has common properties.

Attributes - Attributes describe properties of entities and relationships.

Simple:o Attribute composed of a single component with an independent existence.

o Simple attribute cannot be further subdivided.

o For e.g. Gender, Age, Salary etc.

Composite:o Attribute composed of multiple components each with an independent existence.

o Some attributes can be further divided to smaller components with anindependent existence.

For e.g. Address attribute can be composed of composed like Street No., Area,City, Pincode etc.


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Single-values:o Attribute that holds a single value for a single entity.

For e.g. Classroom entity has a single value for the room no. attribute i.e. roomno. is referred as single valued.

Multi-valued attribute:o Attribute that holds multiple values for a single entity.

For e.g. Student attribute can have multiple values for the Hobby attribute-Reading, Music, Movies etc.

o Multi valued attribute may have set of numbers with Upper and Lower limits.

For e.g. Hobby attribute of a student may have between 1 and 5 values. 1 = Minimum

5 = Maximum

Derived:

o Attribute that represents a value that is derivable from the value of a

related attribute or set of attributes.

For e.g. Age attribute can be derived from DOB attribute.

Domain - It is a set of all possible values an attribute can have.

o E.g. Marital Status

o Domain will be Married, Unmarried

Relationships - A relationship is a connection between entity classes. For example, a relationship between PERSONS and AUTOMOBILES could be

an "OWNS"

relationship. That is to say, automobiles are owned by people.

The degree of a relationship indicates the number of entities involved.

The cardinality of a relationship indicates the number of instances in entity class

E1 that can or

must be associated with instances in entity class E2.


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Types of Relationships

One to One (1:1)o For e.g. Employees in the Co. are assigned to their office. i.e. Each Employee =

Unique Office and for Each Office = Unique Employee

One to Many (1:M)o For e.g. A Dept. has many employees and Each employee is assigned to 1 Dept.

Many to One (M:1)

For e.g. Many Employees 1 Dept.


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Many to Many (M:M)

o For e.g. Employees can be assigned to no more than 2 projects at the same time.

Projects must have assigned at least 3 employees.

ER Notation


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Keys - The Key uniquely differentiates one entity from all others in the entity class. A

key is an identifier.

Primary Key - Identifier used to uniquely identify one particular instance of an

entity.

Can be one or more attributes. (consider substituting a single concatenated key

attribute for multiple attribute key)

Must be unique within the domain (not just the current data set)

Value should not change over time

Must always have a value

Created when no obvious attribute exists. Each instance is assigned a value.

Candidate Key - when multiple possible identifiers exist, each is a candidate key

Concatenated Key - Key made up of parts which when combined become a uniqueIdentifier. Multiple attribute keys are concatenated keys.

Borrowed Key Attributes - If an is a relationship exists, the key to the more general

class is also a key to the subclass of items. For example, if serial number is a key for

automobiles it would also be a key for trucks.

Foreign Keys - Foreign keys reference a related table through the primary key of that

related table.

Referential Integrity Constraint - For every value of a foreign key there is a primarykey with that value in the referenced table e.g. if account number is to be used in table for

journal entries then that account number must exist in the chart of accounts table.

ACID Test

A- Atomicity

C-Consistency

I-Isolation

D-Durability


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Atomicity refers to the ability of the DBMS to guarantee that either all of the tasks of a

transaction are performed or none of them are. The transfer of funds can be completed or

it can fail for a multitude of reasons, but atomicity guarantees that one account won't be

debited if the other is not credited as well.

Consistency refers to the database being in a legal state when the transaction begins and

when it ends. This means that a transaction can't break the rules, orintegrity constraints,

of the database. If an integrity constraint states that all accounts must have a positive

balance, then any transaction violating this rule will be aborted.

Isolation refers to the ability of the application to make operations in a transaction appear

isolated from all other operations. This means that no operation outside the transaction

can ever see the data in an intermediate state.

Durability refers to the guarantee that once the user has been notified of success, the

transaction will persist, and not be undone.

Types of DBMS

There are mainly following types of three database

Hierarchical Database

Network Database

Relational Database

Explanation

Hierarchical Database: Develop in 1950s.

One of the Oldest Database model.

Developed jointly by North American Rockwell Company and IBM.

Hierarchical Model is a tree structure with record forming the nodes and fields forming

the branches of the tree.

Organization of Data

Hierarchical Model Organizes the Data Elements as Tabular rows, one for each instanceof entity.

For e.g. At the Top we have a GM, under him we have several DGM. Each DGM looks

after a couple of Departments and each Dept. will have a Manager and many Employees.

o Represent in Hierarchy.

o Dependent records are there.


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Example:

Structure of a Family:

Parents can have many children:

1 to Many relationship The Great Grandparent is known as ROOT of the Tree.

The Grandparents and children are the NODES or Dependents of the Root.

Root may have number of dependents.


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Operations on Hierarchical Model:

Insert Operation:

It is not possible to insert information which does not play any part i.e.

Node cannot exist without a Root but Root can exist without Node i.e. Parent can

exist without Child.

Update Operation: Update anomalies exist for Children not for Parent.

Delete Operation:

Deletion of Parent causes the deletion of Child records.

Retrieve Operation:

Retrieval methods are Complex and Asymmetric.

Hierarchical Model suffers from the Insertion Anomalies, Update

Anomalies and Delete Anomalies; also the retrieval operation is Complex and

Asymmetric.


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Advantages:

Simplicity:

Database is based on Hierarchical structure.

Data Security:

It was the 1st model that offered data security.

Data Integrity:

Hierarchical model is based on Parent/Child relationship i.e. link between Parent Child

segments. Child is automatically referred by its Parent.

Efficiency:

Efficient in displaying large number of 1 to Many relationships.

Disadvantages:

Cannot handle Many-Many relations

Can not reflect all real life situations

Anomalies in insert delete and update operations.

Network Model:

This model replaces the Hierarchical Tree with a Graph.

Allows more general connections among the Nodes. It handles Many to Many relationship.

For e.g. Employee work for 2 Department.

Handles non-hierarchical relationships.

Allows 1:1, 1:M and M:M relationship.

In network database terminology, a relationship is a SET.

Each set is made up of 2 types of Records.

An Owner Record (Parent) and a Member Record (Child).

In addition to the part and supplier record types, a 3rd record type is introduced i.e.

Connector.


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Operations on Network Model:

Insert Operation:

o New record can be inserted in the database by joining with a

Connector/Pointer.

Update Operation:

o No search criteria is needed to update a record, rather simply updating is

performed for record.

Delete Operation:

o In order to delete any record the corresponding pointers and connectors

are also deleted.

Retrieve Operation:

o Retrieval method for network model are Symmetric but complex.

Advantages:

Conceptual Simplicity:

o Conceptually simple and easy to design.

Capability to handle more relationship types:

o Network model can handle 1:M and M:M relationships.

Ease of data access:

o Data access is easier and flexible than hierarchical model.

Data Integrity:

o Member cannot exist without a Owner.

Data Independence

Database Standards:

o It is based on standards by ANSI/SPARC. (DDL & DML)(American National Standards Institute/Standards Planning and Requirements

Committee).


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Disadvantages:

System Complexity:

o All records are maintained using Pointers i.e. whole database structure becomes

complex.

Operational Anomalies:

o Due to usage of large number of pointers, implementation becomes complex and

complicated.

Absence of Structural Independence:

o If changes made in database structure then all application programs need to be modified

in order to access data.

Relational Model

Stores data in the form of tables.

Concept purposed by Dr. E.F. Codd, a researcher of IBM in the year 1960s.

Consist of 3 major components:

Set of Relations and set of Domains, that defines the way data can be

represented (Data Structure).

Integrity rules that define the procedure to protect the data (Data Integrity).

Operations that can be performed on data (Data Manipulation).

Definition: A relational model database is defined as a database that allows the user to

group its data items into one or more independent tables that can be related to one another

by using fields common to each related table.

Characteristics Whole data is conceptually represented into Rows and Columns, called a

Relation or Table.

All values are Scalar i.e. at any given row/column position in a relation there is

one and only one value.

All operations are performed on relation.


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Basic Terminology used

Tuples of a Relation:

o Each row of data is a tuple.

Cardinality of a Relation:

o No. of tuples in a relation is cardinality.

Degree of a Relation:

o Each column in the tuple is called an attribute. The no. of attributes in a

relation determines its degree.

Domains:

o Set of all possible values that an attribute contain. E.g. Age, Gender,

Degree type etc.

Body of a Relation:

o A table to qualify as a relation each record must be uniquely identifiable

and table must contain no duplicate records.

Keys of a Relation:

o It is a set of one or more columns whose combined values are unique among all

occurrences in a given table. A key is the relational means ofspecifying

Uniqueness.

Type of keys are:

Primary Key

Foreign Key

Types of Keys:

o Primary Key:

It is an attribute or a set of attributes of a relation which posses the

properties ofUniqueness.

For e.g. Roll_No attribute in Student table is a Primary Key.

o Foreign Key:

It is an attribute of a table, which refers to the primary key of some

another table. Foreign key permit only those values, which appears in theprimary key of the table to which it refers.


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Operations in Relational Model

Insert Operation:

o For e.g. information of Supplier who does not supply any part can be

inserted without any anomaly.

Update Operation:

o For e.g. In Student table if a student changes address than it can simply be

changed from Ludhiana to Moga.

Delete Operation:

o Information can be deleted from relation easily without affecting other

records.

Retrieval Operation:

o Retrieval operation is simple and symmetric.

Advantages:

Structural Independence:

o Changes in the database structure do not affect the data access.

Conceptual Simplicity:

o Simpler at conceptual level.

Design, Implementation, Maintenance and Usage ease:

o Due to both data independence and structure independence makes database

design, implementation, maintenance and usage easier than other models.

Ad hoc query Capability:

o With SQL it becomes very easy to use.

Disadvantages:

Hardware Overheads:

It requires powerful hardware computers and data storage devices.

Ease of design can lead to bad design:

Its easy to use but as database grows, poorly designed databases will slow the

system and will result in performance degradation and data corruption.


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Information island Phenomenon:

Due to easy to implement and use, many people or departments will create their

own databases and applications which will prevent information integration which will

cause data inconsistency, data duplication and data redundancy.


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CHAPTER 3

HTML


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Introduction to web designing

Web design is the skill of creating presentations of content (usually

hypertext or hypermedia) that is delivered to an end-user through the

World Wide Web. It is to create a web sitea collection of electronicfiles that reside on a web. Web design is the skill of creating

presentations of content (usually hypertext or hypermedia) that is

delivered to an end-user through the World Wide Web, by way of a Webbrowser or otherWeb-enabled software like Internet television clients,

micro blogging clients and RSS readers. The intent of web design is to

create a web sitea collection of electronic documents and applicationsthat reside on a web server/servers and present content and interactive

features/interfaces to the end user in form ofWeb pages once requested.

Such elements as text, bit-mapped images (GIFs, JPEGs) and forms can

be placed on the page using HTML/XHTML/XML tags. Displaying

more complex media (vector graphics, animations, videos, and sounds)

requires plug-ins such as Adobe Flash, QuickTime, Java run-time

environment, etc. Plug-ins is also embedded into web page by using

HTML/XHTML tags.


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What is HTML?

HTML (hypertext markup language) -Using this language we can create web page

in the internet. This language is different from c , c++ etc . It provides a means to

create structured documents by denoting structural semantics for text such as

headings, paragraphs, lists etc. as well as for links, quotes, and other items. It

allows images and objects to be embedded and can be used to create interactive

forms. It is written in the form of HTML elements consisting of "tags" surrounded

by angle brackets within the web page content. It can include or can load scripts in

languages such as JavaScript which affect the behavior of HTML processors like

Web browsers; and Cascading Style Sheets (CSS) to define the appearance and

layout of text and other material. The W3C, maintainer of both HTML and CSSstandards, encourages the use of CSS over explicit presentational markup. Using

any web browser like IE, Netscape, Firefox, etc. The result of the execution will

appear as web page.

HTML stands forHyperText Markup Language

An HTML file is a text file containing small markup tags

The markup tags tell the Web browserhow to display the page

An HTML file must have an htm orhtml file extension


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HTML TAGS

Basic Tags

Creates an HTML document

Sets off the title and other information that isn't displayed on the Web page itself

Sets off the visible portion of the document

Header Tags

Puts the name of the document in the title bar

Body Attributes

Sets the background color, using name or hex value

Sets the text color, using name or hex value

Sets the color of links, using name or hex value

Sets the color of followed links, using name or hex value

Sets the color of links on click


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Text Tags

Creates preformatted text

Creates the largest headline

Creates the smallest headline

Creates bold text

Creates italic text

Creates teletype, or typewriter-style text

Sets size of font, from 1 to 7

Sets font color, using name or hex value

Links

Creates a hyperlink

Creates a mail to link

Creates a target location within a document

Links to that target location from elsewhere in the document


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Formatting

Creates a new paragraph

Aligns a paragraph to the left, right, or center

Inserts a line break

Creates a definition list

Precedes each definition term

Precedes each definition

Creates a numbered list

Precedes each list item and adds a number

Creates a bulleted list

Precedes each list item and adds the bullet

A generic tag used to format large blocks of HTML; also used for stylesheets


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Graphical Elements

Adds an image

Aligns an image: left, right, center, bottom, top, middle

Sets size of border around an image

Inserts a horizontal rule

Sets size (height) of rule

Sets width of rule in percentage or absolute value

Creates a rule without a shadow

Tables

Creates a table

Sets off each row in a table

Sets off each cell in a row

Sets off the table header (a normal cell with bold, centered text)

Table Attributes

Sets width of border around table cells


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Sets amount of space between table cells

Sets amount of space between a cell's border and its contents

Sets number of columns a cell should span (default=1)

Sets number of rows a cell should span (default=1)

Frames

Precedes the tag in a frames document; can also be nested in other framesets

Defines the rows within a frameset, using number in pixels or percentage of width

Defines the columns within a frameset, using number in pixels or percentage of

Defines a single frame within a frameset

Defines what will appear on browsers that don't support frames

Frames Attributes

Specifies which HTML document should be displayed

Names the frame so it may be targeted by other frames

Defines the left and right margins for the frame; must be equal to or greater than1


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Defines the top and bottom margins for the frame; must be equal to or greater than 1

Sets whether the frame has a scroll bar; value may equal "yes," "no," or "auto."

Forms

Creates all forms

Creates a scrolling menu. Size sets the number of menu items visible before you need to

scroll.

Sets off each menu item

Creates a pulldown menu

Sets off each menu item

Creates a text box area - columns set the width; rows set the height.

Creates a checkbox - text follows tag.

Creates a radio button - text follows tag.


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CSS (Cascading Style Sheets)

Style sheets are powerful mechanism for adding styles (e.g. fonts, colors, spacing) to web

documents.They enforce standards and uniformity throughout a website and provide numerous

attributes to create dynamic effects.

With style-sheets, text and image formatting properties can be predefined in a single list.

The advantages of the style sheet include the ability to make global changes to all

documents from a single location.

Style sheets are said to Cascade when they combine to specify the appearance of a page.

What is CSS?

CSS stands forCascading Style Sheets

Styles define how to display HTML elements

Styles are normally stored in Style Sheets

Styles were added to HTML 4.0 to solve a problem

External Style Sheets can save you a lot of work

External Style Sheets are stored in CSS files

Multiple style definitions will cascade into one

Syntax:

Tag

{

attribute: value;

attribute:value;

}

The selector is normally the HTML element/tag you wish to define, the property is theattribute you wish to change, and each property can take a value. The property and value

are separated by a colon, and surrounded by curly braces:


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The class Selector

With the class selector you can define different styles for the same type of HTML element.

Say that you would like to have two types of paragraphs in your document: one right-

aligned paragraph, and one center-aligned paragraph. You have to use the classattribute in your HTML document:

.right

{

}

This paragraph will be right-aligned.

This paragraph will be center-aligned.

The id Selector

You can also define styles for HTML elements with the id selector. The id selector isdefined as a #.The style rule below will match the element that has an id attribute with a

value of "green":

#green {color: green}

How to Insert a Style Sheet

When a browser reads a style sheet, it will format the document according to it. There are

three ways of inserting a style sheet:

External Style Sheet

An external style sheet is ideal when the style is applied to many pages. With an external

style sheet, you can change the look of an entire Web site by changing one file. Each

page must link to the style sheet using the tag.

The tag goes inside the head section:


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The browser will read the style definitions from the file mystyle.css, and format the

document according to it. An external style sheet can be written in any text editor. The

file should not contain any html tags. Your style sheet should be saved with a .css

extension. An example of a style sheet file is shown below:

hr {color: red}

p {margin-left: 20px}

body {background-image: url("images/back40.gif")}

Internal Style Sheet

An internal style sheet should be used when a single document has a unique style. You

define internal styles in the head section by using the tag, like this:

hr {color: red}

p {margin-left: 20px}body {background-image: url("images/back40.gif")}

The browser will now read the style definitions, and format the document according to it.

Inline Styles

An inline style loses many of the advantages of style sheets by mixing content withpresentation. Use this method sparingly, such as when a style is to be applied to a single

occurrence of an element.

To use inline styles you use the style attribute in the relevant tag. The style attribute can

contain any CSS property. The example shows how to change the color and the left

margin of a paragraph:


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This is a paragraph

Introduction to JavaScript

JavaScript is a scripting language

A scripting language is a lightweight programming language

JavaScript was designed to add interactivity to HTML pages

JavaScript is usually embedded directly into HTML pages

JavaScript is an interpreted language (means that scripts execute without preliminary

compilation)

Everyone can use JavaScript without purchasing a license JavaScript is adds functionality, validate forms, detect browsers, and much more.

JavaScript is the most popular scripting language on the internet, and works in all major

browsers, such as Internet Explorer, Firefox, Chrome, Opera, and Safari.

JavaScript gives HTML designers a programming tool - HTML authors are normally

not programmers, but JavaScript is a scripting language with a

very simple syntax!

OPERATORS IN JAVASCRIPT

JavaScript Arithmetic Operators

Arithmetic operators are used to perform arithmetic between variables and/or values.

Given that y=5, the table below explains the arithmetic operators:

Operators -

j Addition x=y+2

x=7

j Subtraction x=y-2

x=3

j Multiplication x=y*2


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x=10

j Division x=y/2

x=2.5

j Modulus (division remainder) x=y%2

x=1

j Increment x=++y

x=6

j Decrement x=--y

x=4

JavaScript Assignment Operators

Assignment operators are used to assign values to JavaScript variables. Given that x=10

and y=5, the table below explains the assignment operators:

Operators-

=

x=y

x=5

+ =

x+=y x=x+y

x=15

-=

x-=y x=x-y

x=5

VARIABLES IN JAVASCRIPT


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As with algebra, JavaScript variables are used to hold values or expressions. A variable

can have a short name, like x, or a more descriptive name, like carname.

Rules for JavaScript variable names:

Variable names are case sensitive (y and Y are two different variables)

Variable names must begin with a letter or the underscore character

Note: Because JavaScript is case-sensitive, variable names are case-sensitive.

Declaring (Creating) JavaScript VariablesCreating variables in JavaScript is most often referred to as "declaring" variables. You

can declare JavaScript variables with the var statement:

var x;

var carname;

After the declaration shown above, the variables are empty (they have no values yet).

However, you can also assign values to the variables when you declare them:

var x=5;

var carname="Volvo";

After the execution of the statements above, the variable x will hold the value 5, and

carname will hold the value Volvo.

Note: When you assign a text value to a variable, use quotes around the value.

JAVASCRIPT EVENTSHTML 4 added the ability to let events trigger actions in a browser, like starting a

JavaScript when a user clicks on an element.

Below is the standard event attributes that can be inserted into HTML / XHTML

elements to define event actions.

and Events

The two attributes below can only be used in or :


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Attribute Value Description

Onload Script Script to be run when a

document load

Onunload Script Script to be run when adocument unload

Form Events


Onbhur Script Script to be run whenan element losses

focus

Onchnge Script Script to be run whenan element change

Onfocus Script Script to be run when

an element gets focus

Onreset Script Script to be run whena form is reset

Onselect Script Script to be run when

an element is selectedOnsubmit Script Script to be run when

a form is submitted

Mouse Events


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Onclick Script Script to be run on a

mouse click

On doubleclick Script Script to be run on amouse double-click

Onmouse down Script Script to be run when

mouse button is

pressed

On mouse move Script Script to be run when

mouse pointer moves

Onmouseout Script Script to be run when

mouse pointer moves

out of an element

Onmouseover Script Script to be run when

mouse pointer moves

over an element

onmouseup script Script to be run when

mouse button is rele

Keyboard Events


On key down Script Script to be run when

a key is pressed

Onkeypress Script Script to be run when

a key is pressed and

released

Onkeyup Script Script to be run whena key is released


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CHAPTER 4

OPERATING SYSTEM

Operating System


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Operating SystemOperating systems perform basic tasks, such as recognizing input from the keyboard,

sending output to the display screen, keeping track of files and directories on the disk,

and controlling peripheral devices such as disk drives and printers. Process management,

Memory management, Resource management and Security management.

Classify an operating system

Operating systems can be classified as follows:

Multi-User: Allows two or more users to run programs at the same time. Some

operating systems permit hundreds or even thousands of concurrent users.

Multiprocessing: Supports running a program on more than one CPU.

Multitasking: Allows more than one program to run concurrently.

Real Time: Responds to input instantly. General-purpose operating systems,

such as DOS and UNIX, are not real-time.

Batch processing is a system in which a group of similar tasks is collected and

they are collectively send for processing and output is generated on punched cards

and given to the users who generated the tasks.

Time-sharing operating systems a computer provides computing services to

several or many users concurrently on-line. The user, in this environment, has

nearly full interaction with the program during its execution, and the computers

response time may be expected to be no more than a few second

Real time operating systems is designed to service those applications where

response time is of the essence in order to prevent error, misrepresentation or even

disaster. Examples of real time operating systems are those, which handle airlines

reservations, machine tool control, and monitoring of a nuclear power station. The

systems, in this case, are designed to be interrupted by external signal that require

the immediate attention of the computer system.

Deadlock Definition


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A set of processes is deadlocked if each process in the set is waiting for an event that onlyanother process in the set can cause (including itself).

Conditions for Deadlock

o Mutual exclusion: resources cannot be shared.o Hold and wait: processes request resources incrementally, and hold on to what they'vegot.

oNo preemption: resources cannot be forcibly taken from processes.o Circular wait: circular chain of waiting, in which each process is waiting for a resource

held by the next process in the chain.

Process Management

The CPU executes a large number of programs. While its main concern is the execution of user

programs, the CPU is also needed for other system activities. These activities are calledprocesses. A process is a program in execution. Typically, a batch job is a process. A time-shared

user program is a process. A system task, such as spooling, is also a process. For now, a processmay be considered as a job or a time-shared program, but the concept is actually more general

Memory Management

Memory is central to the operation of a modern computer system. Memory is a large

array of words or bytes, each with its own address. Interaction is achieved through a

sequence of reads or writes of specific memory address. The CPU fetches from and stores

in memory.

The operating system is responsible for the following activities in connection with

memory management.

o Keep track of which parts of memory are currently being used and by whom.

o Decide which processes are to be loaded into memory when memory space

becomes available.

o Allocate and de allocate memory space as needed.

Secondary Storage Management


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The main purpose of a computer system is to execute programs. These programs,

together with the data they access, must be in main memory during execution. Since the

main memory is too small to permanently accommodate all data and program, the

computer system must provide secondary storage to backup main memory. Most modem

computer systems use disks as the primary on-line storage of information, of both

programs and data. Most programs, like compilers, assemblers, sort routines, editors,

formatters, and so on, are stored on the disk until loaded into memory, and then use the

disk as both the source and destination of their processing. Hence the proper management

of disk storage is of central importance to a computer system.

The operating system is responsible for the following activities in connection with disk

management

o Free space management

o Storage allocation

o Disk scheduling.

I/O System

One of the purposes of an operating system is to hide the peculiarities of specific hardware

devices from the user. For example, in Unix, the peculiarities of I/O devices are hidden from thebulk of the operating system itself by the I/O system. The I/O system consists of:

o A buffer caching systemo A general device driver code

o Drivers for specific hardware devices.

Only the device driver knows the peculiarities of a specific device

File ManagementFile management is one of the most visible services of an operating system. Computers can store

information in several different physical forms; magnetic tape, disk, and drum are the mostcommon forms. Each of these devices has it own characteristics and physical organization. The

operating system is responsible for the following activities in connection with file management:

o The creation and deletion of files

oThe creation and deletion of directoryo The support of primitives for manipulating files and directories

o The mapping of files onto disk storage.

Protection System


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The various processes in an operating system must be protected from each others activities. Forthat purpose, various mechanisms which can be used to ensure that the files, memory segment,

cpu and other resources can be operated on only by those processes that have gained properauthorization from the operating system. For example, memory-addressing hardware ensures that

a process can only execute within its own address space. The timer ensures that no process can

gain control of the CPU without relinquishing it.

Distributed System

A distributed system is a collection of processors that do not share memory or a clock.

Instead, each processor has its own local memory, and the processors communicate with

each other through various communication lines, such as high-speed buses or telephone

lines. Distributed systems vary in size and function. They may involve microprocessors,

workstations, minicomputers, and large general-purpose computer systems.

Virtual Memory

In a virtual memory system, the program code deals with virtual addresses. Upon use, the

virtual address is translated by the mmuto obtain a physical address that is used to access

physical address.

Physical Memory

Physical Memory (also known as real memory). Physical memory is memory that is

wired to directly to the processor, addressable by physical address.This term is basically

synonymous to main memory, but is used in contrast to virtual memory(1) and backing

store. While moderncomputers usually have lots of virtual memory performance is still

closely related to the quantity of physical memory available. If a system has insufficient

physical memory, it may thrash.

Page Table

In a virtual memory system, it is common to map between virtual addresses and

physical addresses by means of a data structure called a page table. The page number of

an address is usually found from the most significant bits of the address; the remaining

bits yield the offset of the location within the page. The page table is normally indexed by

page number and contains information on whether the page is currently in main memory,

and where it is in main memory or on disk.

MMU


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MMU (also known as Memory Management Unit).The MMU (Memory Management

Unit) is a hardware device responsible for handling memory accesses requested by the

main processor.

PageA virtual memory system usually deals with memory blocks of fixed size as units for

paging. These are known as pages. Pages are often 4 kB or 8 kB in size. This size is

determined by the addressing hardware of the machine.

Page Fault

A page fault is an exception occurring during the translation of virtual addresses to

physical addresses. "Page fault" usually means an access to a page that has been paged

out and hence requires fetching from disk, but it is sometimes also used to mean invalid

page fault or protection fault

PagingIn a virtual memory system, paging is the act of transferring pages between physical

memory and backing store (usually disk).When pages need to be paged out, a heuristic is

used to select ones that will not be needed soon; "least recently used" is a popular one.

Swapping

Historically, swapping was the technique of moving entire program images to disk (or

drum) and back into physical memory early form of virtual memory nowadays; it is used

as a synonym for Apaging.

Documents

Viva Voice File( Made by Hitakshi Jain Frm Ludhiana)