IST Yearly Notes

Data bases

Components of a Database

-File - A file is a block of related data stored on a storage device (such as an employee database). A file in a database is divided into a set of related records.

-Record - A record is a collection of facts about one specific entry in a database. All the information about one employee is a record. A record is divided into one or more related fields.

-Field - A field is a specific piece of data in a record. Fields for each employee include the employee ID, last name and first name. A field is also known as a data item or category and is made up of characters.

-Character - A character is the smallest unit of data that people can handle and includes letters, numbers and special symbols.

Data Dictionaries

A data dictionary is a comprehensive description of each field in a database. It contains information about the characteristics of each item entered in the database, such as the field names, data types, field sizes and field descriptions – see below –

-Field name is the name of the field; they should beshort, clear and avoid the use of punctuation.

-Field size or field width, is the number of characters allowed ineach field.

-Description specifies the contents of the field.

Data Types

-Data type or field type is the kind of data in the field. Each field stores data of a single data type. Some common data types include:

  • Text - used for text or numbers that do not require calculations
  • Memo - used for lengthy text and numbers such as descriptions
  • Number - used for numeric data to be included in mathematical calculations
  • Currency - used for currency values
  • AutoNumber - Used to create a number automatically when record is added
  • Yes/No –Used for data that can only be of two values, cannot be empty or null
  • OLE object - used for data created in other programs such as a spreadsheet, graphic or sound
  • Hyperlink - used for hyperlinks
  • Date/Time - used for dates and times.

-The organisation of data often involves a key(field to sort and retrieve information).

-A primary key is a field in which each item is unique and must have a value. AutoNumber is a good choice for primary key.

Purpose of:-

-Form

  • A form or label displays data for every field of a single record and the layout can be changed. The user can position fields, headings, instructions and graphics. A well-designed form provides information explaining the required data and any data entry rules that apply to particular fields. For example, a field name ‘Sex (M/F)’ leaves no confusion about its required data. Size, stroke weight and colour of the font impact on the user and the accuracy of the data entered. After one record has been completed the next record appears until all data is entered.

-Table

  • A table or list displays data using columns (fields) and rows (records). You can scroll up & down to view more columns and rows. Good for Several Records or entering new data in only one field. Screen Layout can be changed by adjusting width, height and hiding columns. Data in a table is usually entered using a form, retrieved using a query and printed using a report.

-Query

  • A query is a search of a database for records that meet a certain condition. It is a question you ask of the database. The results of a query are displayed in a table but can be used as the basis for a form, report, graph or another query.

-Report

  • The purpose of the report will determine its content, format and style. Before creating a report the user may need to select the required records by constructing a query.

Difference between Searching and Sorting

-Searching

  • Searching is the process of locating data and information. For small databases the ‘Find’ or ‘Search’ commands are adequate but for large databases you should construct a query.

-Sorting

  • Sorting is the process of arranging data in a particular order (organising data).Sorts can be performed in either ascending or descending order

Methods of Editing Data

Editing is changing data. (Inserting, Deleting, Changing or Modifying Data structure)

-Inserting Data.New records can be inserted by the correct command. Records can be rearranged by sorting.

-Deleting Data. To delete a record, the user selects the records and then presses the Delete key or chooses an appropriate command.

-Data is moved and copied using the Cut, Copy and Paste commands.

-The structure of the database can be edited to meet new requirements. This involves changing the data dictionary.

Internet

Difference between Internet and Intranet

-Internet –

  • The Internet is a connected set of networks using the TCP/IP standard with millions of computers linked all around the world. Provides intstant access to information (news, weather, sports, share prices and educational materials). Also provides services - Sending messages, banking, shopping, playing games and listening to music. Access to the internet is available from almost anywhere around the world through an ISP.

-Intranet

  • An intranet is a private network that uses a similar interface to the Internet existing within an organization.Intranet supports email, newsgroups, file transfer, web publishing with access through a web browser.

Parts of a URL

A URL (Uniform Resource Locator) is the address of a file or resource on the Web in a lower case, single unbroken line without spaces.

There are three parts to a URL:

-Protocol—indicates access to a particular resource on the Web. For most cases the protocol will be It allows access to web pages based on hypertext.

-Domain name—address of the specific computer where the resource is located such as The domain name is interchangeable with the IP address.

-File path—full path to the file to be retrieved. It may be a simple file name or a directory path, such as /heinneman/default.htm. The domain name and the file path are separated by a forward slash (/). The file being retrieved in this example is default.htm.

Main Parts of an Email Header

-To—main person receiving the message

-Cc—carbon copysends the same message to other people just as information for them

-Bcc—blind carbon copy sends a copy to other people without revealing who else got the message

-Subject—is the topic of the message or brief description—this is very useful for the receiver of the message, also displayed outside for the person to click on.

Email attachments

-An attachment is a file in its original condition and format that is sent with the email message. When sending an attachment it is important to include a brief explanation in the main body of the email message. The file name and the format of the attachment should be easily understood.

Netiquette

-Netiquette is a code of acceptable behaviour users should follow on the Internet. It covers rules for all aspects of the Internet such as the email, chatting, newsgroups and discussion groups. Some of the rules for netiquette include:

  • keep messages short and to the point
  • be polite and avoid offensive language
  • avoid sending abusive or insulting messages (flames)—do notparticipate in flame wars
  • avoid using all capital letters as it is considered shouting
  • use emoticons to express feelings such as :) for happy or :( forsad
  • use abbreviations and acronyms such as ‘IRL’ for ‘in real life’ or‘BTW’ for ‘by the way’
  • Make the email subject line as meaningful as possible.

Search Engines and how they work

-A search engine is a program that finds websites and web pages. It accesses a database of indexed websites that can be searched using a keyword. This index is built by regularly scanning for new websites and accepting submissions from website authors.

-A web directory organises the Web into categories and then smaller subcategories. This allows the user to browse through the categories until theyfind a relevant site.

-Most search engines allow users to search for specific items such as images.

-Some search engines allow a search to be restricted to just Australia

-Advance search options provide users with more accurate results. (Such as restricted to files that were updated recently, particular file formats or sites without certain words)

Internet Protocols

-A protocol is a set of rules that governs the transmission of data between computer devices; protocols include TCP/IP, HTTP, FTP and SMTP.

-Transmission Control Protocol/Internet Protocol (TCP/IP) is a common language for data transmission and error detection across the Internet. It works by breaking information into smaller packets of data. Each data packet contains the information and the address of the receiving computer. The TCP tells what is in the packet and IP tells the receiving computer where and how to send the packet.

-Hypertext transfer protocol (HTTP) is a standard for transferring the contents of a web page into a browser for viewing. Does not download files that make up the web page. HTTP is a one-way system as data is only transferred from the web server to the browser.

-File transfer protocol (FTP) is a standard to upload and download files. An FTP server is a computer that allows users to upload and download files using FTP. FTP is a file server not a web server.

-Simple mail transfer protocol (SMTP) is a standard for outgoing email. Most email messages are sent using SMTP. POP3 (Post Office Protocol) is a standard for incoming email.

Cookie

-A cookie is a file that is stored on the hard disk after the user visits a website. It is used to measure a user’s behaviour and work flow habits. Cookies store the information about the web pages visited and the transactions completed. However, most cookies are designed to improve your experience and allow organisations to target advertisements to your tastes. Users have the option to block or accept cookies.

Proxy Server

-A proxy server is a barrier to the Internet to ensure users are securely and productively accessing network resources. It lets administrators limit access to objectionable content by filtering URLs. Proxy servers distribute and manage information reducing network traffic and user wait times. Traffic time is reduced as the proxy server caches frequently accessed documents or entire websites.

Firewalls

-Firewalls are used on the Internet or any network to check all incoming data for the purpose of verification and authentication. It aims to protect a computer system from hackers trying to access sensitive information. Firewalls are an important security measure on an intranet. All messages entering or leaving the intranet pass through the firewall. It examines each message and blocks those that do not meet the specified security criteria.

Antivirus Software

-Anti-virus software is used to scan a file or disk for a range of known viruses. A virus is a small program that attaches itself to an application. There is no guarantee that anti-virus software will stop every virus, as new viruses are constantly appearing. However, if users download the latest virus definition files and regularly use the anti-virus program, it will minimise the problem

Website Development

-Types of Web Pages and Purpose

  • Home Page
  • Home page (index page) is the first page viewed by a visitor and provides information about the purpose and subject matter of the website; it provides a link to other web pages.
  • Intermediate Page
  • An intermediate page is the next level down from the home page. It provides link back to home page.They provide structure and assist in the navigation of the website. Way of grouping Content pages.
  • Content Page
  • Content pages contain topic details and are usually accessible from intermediate pages. Content pages usually contain a link to home page.

Features of a Website

-Contact information—Information such as address, phone, fax and email.

-Text—Look and style is important. Should display the essential content.

-Graphic—Add interest and attraction. Most common formats are JPEG and GIF.

-Thumbnail image—small preview of the ‘real’ full size image. Downloads faster than the full size image. Viewer can click the thumbnail to view full size image.

-Rollover—picture, icon or button that changes when the mouse is moved over it. A rollover is 2 images. GIF is mostly used as it needs to be changed quickly.

-Animation—a flashing object to get visitor’s attention. Animation is usedto direct the visitor to an area of the screen or an interesting feature.

-Streamed audio—used to provide background music or sound effects. Streaming audio is heard before the entire file has been transferred.

-Streamed video—video clips that play before the entire file has been transferred. It is more dependent than streamed audio on a high bandwidth.

-Hyperlink—link to another part of the same web page or web site. Hyperlinks are made using text (hot word) or image (hot spot).Hyperlinks are usually underlined or coloured.Often arranged in horizontal rows or vertical columns to form a navigation toolbar.

-Tables—rows and columns of cells that are filled with characters or graphics. Used to arrange information in row and column format, borders and shading can be applied.

-Lists—unordered lists do not have a numbered sequence. Entry in an unordered list is usually shown with a bullet. Ordered lists use a numbered sequence.

-Frames—space or boxes that hold an object. Each frame is considered a separate window and could be a separate HTML document. Frames allow a banner, advertising message or animation to be held in place while the visitor navigates the website.

-Web forms—are tools to collect information, such as orders for goods and services and results from surveys. Web forms have an invisible part that processes the data and stores it in a database.Information is entered using text boxes, option buttons, check boxes, list boxes, spin boxes.

Design Considerations for a website

  • Consistency—layout, format and style should be the same throughout the website unless different data types demand a change. Readability is improved when similar items are grouped.
  • Navigation—Colouring different areas of the page, using visual symbols (icons and arrows), inserting clear page headers and creating simple hyperlinks improves navigation.
  • Simplicity—do not overuse design elements as this will create visual clutter and confuse the visitor. The overuse of colour, sound and animations can be distracting. First impressions on the Web are important. A visitor often forms an opinion of a website within the first minute of accessing the home page.

-Design Factors

  • Text—clear and legible text using at most three different fonts. Care should be taken using font styles such as bold and italic. Underlining is only used for hyperlinks. Long lines of text are difficult to read.
  • Colour—many different colours can be distracting and reduce readability. A colour scheme should not interfere with the main message of the web page. Dark text on a light background or vice versa usually works well. Blue is often preferred for unused links and purple for used links.
  • Graphics—are used to create interest, however, they are slow to download. When using graphics consider the size of the graphic, recognisable icons and whether the graphic fits easily on the screen.
  • Animation—visitors seeking information from a website are distracted by inappropriate animation. A small creative animation such as a comet-type effect can be effective.
  • Audio and video—should not be an essential part of a web page as some visitors might not have the right hardware or plug-in. It is good practice to advise visitors about the size of audio and video files.

Networking

Advantages and Disadvantages of setting up a network

-Advantages

  • Sharing peripheral devices: Share Printers, Hard disks and Internet access.
  • Sharing applications: Networks enable users to share applications. Usually a network licence is cheaper and can be installed faster.
  • Sharing data: Networks provide a very fast method for sharing and transferring files. Many networks have a file server to store data which can be accessed from any computer on the network. This increases productivity and efficiency.
  • Security of information: Networks secure files by restricting access to only authorised users. The entire network is backed up on a regular basis. Firewalls are used to protect data on the network from hackers and unauthorised users.
  • Improved communication: Networks enable users to work together in ways that otherwise would not be possible with Email and messaging systems.There is also a range of software designed for groups of users on a network. One example of this software is project management software. It is a tool to efficiently plan, manage and communicate information about a large project.

-Disadvantages

  • Expensive to install: Servers, network devices, cables and network software are expensive. Technician will be required to setup a network but saves money over time.
  • Administrative time: Maintenance requires time and a person called a Network Admin to be employed for looking after the network.
  • Server failure: If the server fails no one can access the network and its devices and productivity can be lost.
  • Damaged equipment: One network cable can stop the entire network from functioning.A faulty network Interface card will stop a user from accessing the network.
  • Maintaining security: Networks are targets for hackers and viruses. The files stored on a network can be accessed, stolen and edited more easily than files stored on an individual computer. A virus that enters the network can spread to every computer on the network. Appropriate procedures need to be implemented to maintain security such as corporate anti-virus software and powerful firewalls.

Protocols used over Networks