Types of search engines

There are different types of search engines.

1) Crawler / Spider or robot based search engines - Search engines like google and yahoo has their own spider or crawler software which automatically visits and collects data of different websites and this data gets included and indexed in search engine database . Each search engine has its own algorithm to have ranking of these websites and display the search results.

2) Search Directories - has categories and subcategories for listing the websites. One can submit his website to suitable category and then it is reviewed by human editors and then they decide the listing and ranking of the website. e.g. dmoz.org , dir.yahoo.com

3) Meta search engines - This type of search engines searches the major search engines like google, yahoo , ask.com , bing etc. simulatnously at a time and displays the combined result on search engine result page (SERP) . e.g. dogpile.com

4) Specialized search engines - These are search engines for specific niche area.
e.g. to search books we have books.google.com
To search blogs we have blogsearch.google.com
To search articles we have scholar.google.com

Types of email services

Different types of email services are available like

1) Web based email service or online email service e.g. yahoo free mail service

2) POP3 email service - Post Office protocol email services can be configured in softwares like Outlook express , Eudora installed in local PC of email service user and emails can be send /received from mail boxes of this software.

3) IMAP - Internet Message Access Protocol

Sharing of Internet Connection

A single internet connection connected to one computer on a LAN can be shared with other computers in LAN. Sharing of Internet Connection is possible by using

1) Hardware - 1) ADSL/ DSL router with more than one port
- 2) Switch or Hub used for LAN

2) Software - 1) Operating systems like Windows 98 and windows XP support the internet connection sharing.

2) Proxy server software can be installed on machine having internet connection for sharing.
e.g. AnalogX

Types of Internet connection

Internet is wide area network throughout the world where user connected to internet can get the information from websites hosted on web servers or can use services like email, video, audio, voice chat etc.

Internet service providers are called ISPs

There are different types of internet connections available.
1. Dial up connection - Uses dial up modem and telephone line which can provide speed upto 56.6kbps.

2. Broadband connection - Uses ADSL or DSL router and copper wire telephone line coming from nearby telephone exchange. Can provide data transfer speed upto 2mbps or more. Voice and internet data transmission can work simultaneously with this technology. Many broadband connection uses CAT 5 or CAT 6 cable from nearby server to user PC.

3. ISDN - Integrated Services Digital Network

4. T1

5. T2

6. Wireless Internet

7. GPRS- General Packet Radio service - This type of internet is used in cellphones. Connection speed possible is in the range of 116kbps.

Data Communication components

Data Communication components are all the devices /components involved in communication.

Typically this components can be classified as

1) Data or message
2) Sender
3) Receiver
4) Transmission media or medium
5) Protocol - set of rules for communication.

Wireless LAN

Components of a Wireless LAN are

1) Wireless Router
2) Wireless Network card
3) Access point or Repeater

Wireless LAN uses 802.11a,b, and g standards .

WLANs have data transfer speeds ranging from 1 to 54 mbps.

The 802.11n standard can reach 300 to 600 mbps.

A WLAN signal can be broadcast to cover an area with radius of 65 to 300 feet.

Because the wireless signal is broadcast so everybody nearby can share it, several security precautions are necessary so that only authorized users can access WLAN.

Network Media - Wired and wireless and WLAN

Wired Media
1. Coaxial cable - RG58
2. Twisted pair cable - CAT 5 , CAT 6 (CAT means category)
There are four pairs of twisted cable within a CAT 5 cable.
3. Fiber Optics


Wireless Medium/Media

Wireless communication is broadcast through free space without using a physical conductor.It is in the form of electromagnetic waves.

The electromagnetic spectrum ranging from 3khz to 900 THz is used for wireless communication.

Radio Waves - The electromagnetic waves ranging in frequencies between 3KHz to 1 GHz are called radio waves. They are used for AM FM radio , television , cordless phone etc.

Microwaves - Electromagnetic waves between 1 and 300 GHz are called microwaves. Applications are cellular phones, Satellite Networks and wireless LAN

Infrared waves - Frequencies from 300 Ghz to 400 Thz . It is used for short range communication.

Components of a Wireless LAN are

1) Wireless Router
2) Wireless Network card
3) Access point or Repeater

TYBcom Syllabus for Computer Systems and Applications

Unit 1 - Data Communication, Networking and Internet
Unit 2 - E- Commerce
Unit 3 - Database and SQL
Unit 4 - Introduction to C programming OR Visual Basic
Unit 5 - Spreadsheet (MS Excel)