Manipulating Data

Manipulating Data

A set of relational operators have been defined to manipulate relational databases. Basic data manipulation operators include select, project & join.

Select - eliminate rows according to certain criteria.

A select operation reduces the length of a table by filtering out unwanted rows. By specifying conditions in the where clause, the user can filter unwanted rows out of the result set, the select operation reduces the results vertically.

Project - eliminate columns in a table.

Just as the select operation reduces the number of rows, the project operation reduces the number of columns. The column names specified in the SQL select determine those columns that are displayed,  the project operation reduces the size of the result set horizontally.

Join - combine two or more tables.

A join operation such as used to relate two or more independent tables that share a common column. In a join, two or more independent tables are merged according to a common column value.

Data organize in tables can be easy to manipulate and one of the primary advantages of a relational database is that it allows tables to be linked using common data attributes, which help to produce useful information and reports and also allows users to relate data in new ways without having to redefine complex relationships.

Data Manipulation Language (DML) commands are used to manipulate the data in database. The DML, with the DBMS allows database users to access, modify and make queries about the data that contained in the database.

SQL (Structured Query Language) is the data manipulation language for relational databases. Once a database has been set up and loaded with data, it can produce desired reports, documents and other outputs. By the output control feature a database program allows to select the records and fields to appear in reports.

Impact of the internet

Impact of the internet

The internet creating a big impact on the society by revolutionizing the way people live and work in the everyday life. There huge impact in several keys areas like the government sectors.

E-government, E-commerce, E-learning, and E-entertainment are five examples of the change internet brought to our society.

The cost of some of services cloud bring to zero once they are providing through the internet for example, consider voice calling to long distance location through the internet.

Ultimately, we hope the internet would bring people, service and different cultures together in to a small village

(E.g. Facebook,)

History of the internet

The internet began as a research project funded by ARPA. Researchers studied ways to interconnect computers that use various kind of network. The name internet refers to both the project and prototype network system that researchers built.

Known by the name TCP/IP the software used to make the internet operate contains many complex computers programs that work together to provide communication. The software work so well that it hides the details of under laying hardware and provides the illusion of a seamless system.

The internet an open system, because the specification needed to build TCP/IP software or use of the internet are available to everyone. Researchers who devised the internet published technical information in the series of reports that describe the internet and the TCP/IP software it uses. For historical reasons, each document in the series is labeled request for the comments.

Word Processing

Introduction to Word Processing

What is Word Processing?

When you are creating a document, you may need to;

• Edit and format text
• Insert and format tables, graphics, charts and objects from other applications
• 
  

That is, you need to process the document.

Typing/Inserting editing and formatting text, graphic and other objects is simply termed as "Word Processing".

Applications help you to do these tasks are called as Word Processing Applications.

Word Processing Applications

Today there are two most popular and commonly used Word Processing Applications.

• Microsoft Word
• Open Office—Writer

Microsoft Word runs only with MS Windows environments where Open Office-Writer runs with Open Source Operating Systems like LINUX as well as with MS Windows.

History

History of Word processing goes beyond the age of computer starting form the
typewriter. The term "Word Processor" was first used by the IBM in 1964 in their MT/ST (Magnetic Tape / Electric Typewriter).

In 1969 IBM introduced MagCards (Magnetic Cards) to record, recall and reprint the text once typed.
In: 1970 IBM produced Word Processing Systems using floppy disk for storage. In 1977
the disk Based Word processing applications were introduced.

1^st Word Processing Application for PC is called Easy-Writer. Next, came the Word Star,
the ware Perfect ...etc. and now there are lots of Word Processing Applications in the
world. Those are been developed based on the operating system on which they should
run.

Examples

Easy-Writer, Word Star, Word Perfect, Ability Writer, 
KWord, LyX, Open Office Writer, MS Word.

Devices Of the Computer

Input devices

Any device that can feed data or information to a computer system is referred to as an input device.

The user can use devices like the keyboard, mouse or trackball and joystick to provide commands and data into the computer.

Device like, the microphone, scanner and digital cameras help the processor to receive data from its environment.

Output devices

                     
Any device that can be used to output information from the computer system is known as an output device.

Devices like the Monitor or LCD panel and projectors display information whereas a speaker would provide audible output. A feedback joystick would provide an output which can be felt by the user. Any device that can be used to output information from a computer is known as an output device.

some devices have functionality that fall into both input and output categories.

• Touch-screen display
• A feedback joystick

Storage Devices

Previously data was stored in punch cards (a card with holes punched representing 1s and 0s)

the magnetic tape was one of the earliest forms of data storage device but had a disadvantage since it had to be accessed in a sequential manner.

The introduction of hard disk and floppy disk made it possible for data to be stored and accessed (randomly).

The hard disk was not meant to be portable and was known as fixed disk located inside the computer.

External hard disks were developed but not for the purpose of portability since they were fragile and prone to strong vibrations.

Portable magnetic storage devices like floppy disk had a very limited storage capacity, this was changed with the invention of the ZIP disk which could store over 100 megabytes (1048576 bytes is 1 megabyte).

The invention of the Optical storage disks like the CD ROM and the DVD ROM made it possible to store data on disks which were not affected by magnetic fields, was easier to transport, and cost effective to produce.

The typical CD ROM could store around 700 megabytes whereas the DVD ROM could store in excess of 4.2 gigabytes and now with improved Blu-ray (blue laser) format storage can go up to 27 gigabytes.

The size of all of these disks was somewhat cumbersome (with every device invented in the modern world becoming smaller and much more portable).

With this requirement new disk and memory like the flash-drive (pen drive), SD card, 7 Compact-Flash, Sony Memory stick and the XD picture-card have emerged. Some 3 of these devices have a capacity that could exceed 12 gigabytes and are commonly used for storage in small digital devices

Second generation DBMS’s

Relational Database Model (Second generation DBMS’s)

To overcome the limitation, Edgar F. Codd and others developed the relational data model during the 1970s. This model considered as the second generation DBMS, received widespread commercial accepted during 1980s.

With the relational model, all data are represented in the form of tables. It is based on logical relationship in data, overcame the problems of physical address handling. It is based on mathematical theory and therefor has a solid mathematical foundation. A relatively simple fourth generation language called SQL is used for data retrieval.

• Data Structure: data are store in the form of tabular structure
• Data manipulate: powerful operations are used to manipulate data
• Data integrity: facilities are included to ensure data integrity

Relation: a name two- dimensional table consisting of rows and columns of data. Each relation consists of set of named columns and number of rows (actually a set off tuples).

Employee (Empno, Name, Address)

Empno	Name	Address
1111	Steew	Colombo 5
1115	jone	Colombo 7
1112	Kumara	Colombo 5
1114	Perera	Colombo1

Relational Model Terminologies

Tuple	A row in a relation
Attribute	A  column in a relational
Attribute domain	A set of valid values for an attribute
Degree of a relation	The number of attributes in a relation
Cardinality of a relation	The number of tuples in a relation
Null	Value is not applicable or the value is not known.

Properties of a Relation

• Each relation in a data base must have a unique name.
• An entry at the intersection of each row and columns is atomic or single-valued. (No multi-valued attributes are allowed)
• Each tuple must be unique; no two rows in a relation are identical.  
• Each attribute (or columns) with in a table has unique name.
• The sequence of columns (left to right) is insignificant
• The sequence of rows (top to bottom) is significant

Information Retrieval System

Information Retrieval System

Information can be sent from any computer to any others 24 hours a day. There are various types of resources available for information retrieval.

One major resource is web sites or home pages of organization or individuals like www.bbc.co.uk. Another resource that can be used for information retrieval is search engines. www.google.com is a very popular search engine. You can also find books and reports and repositories of S/W applications and so much more.

Who pay for it?

Who pay for the internet? Do you have to pay for the internet access?

There are no owners for the internet. However, these networks should be developed and maintained by the providers (ISP/IAP). Therefore those who provide network connectivity (internet service providers) have to change individuals/organizations when they want access the internet through their networks.

Generally, there are two type of fees one for access time and the other one for internet connectivity.

Access time is usually based on local telephone charges (e.g. Dial up connection) or a fixed amount irrespective of access time (e.g. ADSL Connection).

In some countries, internet connection can be obtained through cable TV network.

At the same time, an individual or organization can obtain a dedicated direct connection to the internet (e.g. Leased line) if they wont to have very high speed connection and the charges for such connection usually high.

Wireless access is also available from ISP (e.g. HSDPA or 4G) which is much suitable for the mobile user.

Open Office

Introduction to Open Source

• In brief, open source software is which meets the following criteria.Distribution Unrestricted. Open source software can be redistributed either for free or at profit. 
• Source code: The source code (i.e. “Blueprint”) for the software must be made available.
• Derived works: the source code can be used to provide derived works.

What package dose open office comes with?

The following table compare the packages contain in MS Office and those in Open office

Application	MS Office	Open Office
Word Processor	Word	Writer
Spread Sheet	Excel	Calc
Presentation	Power Point	Impress
Database	Access	Base

Word Processor

Open Office writer full-featured word processor. It features unique tools such as navigator and stylist.

These make changing the formatting throughout a large document easy as 1-2-3

Spread Sheet

Open office calc is full-featured spread sheet. It has a vast numbers of statistical and scientific functions.

It can create pivot tables, charts and more

Presentation Tool

Open office impress is a full-featured presentation tool that allows the user to create and modify diagrams and pictures right within the application.

What special features does open office come with.

Open office has a lot of powerful features. These make it a strong competitor with the market leaders.

• MS office compatibility
• One click export to PDF
• Export to flash (.SWF)
• Accessibility
• Support for many native languages
• Open XML file format
• Macro recorder
• 3^rd party add-ons
• ActiveX control
• Support for DocBook and PDA file formats
• Database integration