CS (140) - INTRODUCTION TO COMPUTERS
Teacher: Dr. Shrestha
Materials for class (4)
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GOALS FOR TODAY:
Take examination (3) on materials from Chapters (5) and (6) HOMEWORKS DUE TODAY:
Learn materials from Chapters (7) and (8)
Lecture and Lab
A table on the temperatures created by using WORD
Show your progress on the article on "Photon"
Exercises based on your visit to following websites:
SOUND BLASTER -
MOVIE MAGIC -
WEBTV -
VOICE RECOGNITION -
DVD ENTERTAINMENT SYSTEMS -
JAZ DRIVES -
BUYING A CAR -
INTERNET RADIO -
Web site - http://www.mhhe.com/it/oleary/exercise.mhtml
ASSIGNMENT:
Read and review materials from Chapters (7) and (8)
Test (4) on these materials next class
Exercises on Internet
Use EXCEL to construct a table showing sales by sport and
prepare a 3D graph to display sale volume
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Save days' work in your diskette !
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CHAPTER (7) - COMMUNICATIONS AND CONNECTIVITY
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KEY IDEAS CONNECTIVITY
Connectivity is the act of linking computers and other electronic
devices through communication systems to share access to information
and data. Available connection options include fax machines, e-mail,
voice-messaging systems, video-conferencing systems, shared resources,
and online services.
Fax machines scan images and convert to signals to be transmitted
over telephone lines.
E-mail aka electronic mail is an electronic letter sent between
individuals or computers.
Voice-messaging systems are computer systems linked to
telephones that convert the human voice into digital bits.
Video-conferencing systems allow people located at various
geographic locations to have in-person meetings.
Shared Resources mean sharing expensive hardware and data.
Online Services provide a variety of services including
teleshopping, home banking, investing, travel reservations, and Internet
access. USER CONNECTION
Users often connect to communication systems using standard
telephone lines. The lines typically send and receive analog signals.
Computers send and receive digital signals.
The usual abbreviations that describe the communication speeds are summarized in the table below:
| Unit | Speed |
|---|---|
| bps | bit per second |
| kbps | thousand bits per second |
| mbps | million bits per second |
| gbps | billion bits per second |
Modems
Modems convert digital signals to analog signals and vice versa. Typical
modem speeds are 33.6 and 56 kbps (kilo bits per sec).
The word "MoDem" is made of two words "Modulation" and "Demodulation" contracted.
There are three types of conventional modems:
EXTERNAL - outside the system cabinet connected by cable to serial
port Other Connections
INTERNAL - card that plugs into a slot on the system board
WIRELESS - does not connect to telephone line; receives data through
space
Dial-up connections connect standard telephone line to conventional
modems.
Some connections are all-digital. For example, the special high speed
lines from the telephone companies, T1, T2, T3, and T4
support very high speed transmission without conventional modems. Some
promising new technologies include ISDN (Integrated Services Digital
Network), ADSL (Asymmetric Digital Subscriber Line), Cable modems, and
Satellite/air. COMMUNICATION CHANNELS
Data flows between computers using different channels or media.
The most common are:
DATA TRANSMISSION
Several factors affect how data is actually transmitted from one
point to another. Bandwidth
Bandwidth is the bits-per-second transmission capability of a channel.
Bandwidth may be voiceband (typical speeds - 9,600 to 56,000 bps),
medium band (typical speeds - 56,000 bps to 264,000,000 bps), and broadband
(typical speeds - 264,000,000 bps to 30,000,000,000 bps). Serial and Parallel Transmission
With serial transmission, bits flow in a single continuous stream.
With parallel transmission, bits flow through separate lines
simultaneously. Direction of Data Transmission
Three directions of data flow are simplex, half-duplex, and
full-duplex communications.
Simplex communication - slower and older technology in which
data travels in only one direction.
Half-duplex communication - allows data to flow in both
directions but not simulataneously.
Full-duplex communication - the fastest and becoming the standard
for microcomputer communications. It allows data to travel in both
directions simultaneously. Modes of Data Transmission
Two modes are asynchronous (data is sent and received one byte at a
time) and synchronous (several bytes, a block, are sent at a time). Protocols
A protocol defines rules by which senders and receivers may exchange
information. NETWORK ARCHITECTURE
Network architecture describes how a computer network is configured and
what strategies are used. Terms
Terms often used with networks are: node, client, server, network
opearing system, distributed processing, and host computer.
Configurations
Networks can be arranged or configured in several ways:
Strategies
Every network has a strategy, or way of sharing information and
resources.
Three widely used networking strategies are:
NETWORK TYPES
Networks can be citywide or even international using both cable and
wireless connections. Three network types are: local area networks,
metropolitan area networks, and wide area networks.
Local Area Networks (LAN) - connect devices that are located close
to one another.
Metropolitan Area Networks (MAN) - consist of citywide networks
often using cellular phones.
Wide Area Networks (WAN) - countrywide or worldwide networks. The
Internet is the largest WAN.
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CHAPTER (8) - THE INTERNET AND THE WEB
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KEY-IDEAS
INTERNET APPLICATIONS
The most common Internet applications include communicating,
shopping, researching, and entertainment. ACCESS
Once connected to the Internet, our computer seemingly becomes an
extension of a giant computer that branches all over the world. Providers
The most common access is through a provider or host computer. Three
widely used providers are colleges and universities, Internet Service
Providers (ISPs), and online service providers. Connections
To access the Internet, we need to connect to a provider. Three
types of connections are (1) direct or dedicated, like the ones,
universities have that has a direct link, (2) SLIP (Serial Line Internet
Protocol) and PPP (Point-to-Point Protocol), the kind which uses a
special software along with a high-speed modem and standard telephone
lines to connect to a provider that has a direct link, and (3) terminal, the
cheapest one that uses modem and telephone lines from our end. TCP/IP (Transmission Control Protocol/Internet Protocol)
TCP/IP is a standard protocol of the Internet. When information is
sent over the Internet, it usually travels through numerous
interconnected networks. Before a message is sent, it is broken down
into small parts called "packets". Each packet is then sent separately
over the Internet, possibly traveling different routes to one common
destination. At the receiving end, the packets are reassembled into the
correct order. Protocols control how messages are broken down, sent and
reassembled. E-MAIL
Sending and receiving e-mail is the most common Internet
activity. Basic Elements
E-mail messages have three basic elements: Subject, Addresses and
Attachments.
Another way of describing is, it contains:
Addresses
The Internet uses the Domain Name System (DNS) addressing system for
e-mail. An example, "shrestha@umr.edu" has the first part as the user
name - "shrestha" followed by the domain name - "umr" followed by the
domain code - "edu". DISCUSSION GROUPS
Discussion groups support communication through mailing lists,
newsgroups, chat groups, and instant messging. Four types are:
Discussion group terms include the following:
ELECTRONIC COMMERCE
Electronic commerce, or e-commerce, is buying and selling goods
over the Internet. Web Storefronts
Web storefronts are virtual stores for viewing and selecting goods.
Web storefront creation packages or commerce servers are specialized
packages for creating virtual stores. Web Auctions
Web auctions are similar to traditional auction except that buyers and
seller rarely meet face-to-face. Two basic types are auction house sites
that sell a wide range of merchandise directly to bidders and
person-to-person sites that operate more like flea markets. Electronic payment
Three basic payment options are check, credit card, and electronic
cash (e-cash). SERVICES
There are four basic Internet services: Telnet, FTP. Gopher, and
the Web.
TELNET runs programs on remote computers, FTP uploads and downloads files,
GOPHER provides menus for available resources, and the WEB provides multimedia
interface to Internet resources. BROWSERS
Browsers are programs to access the Web and provide other Internet
services. Two well known browsers are Netscape Communicator and Microsoft
Internet Explorer. Uniform Resource Locators (URLs)
URLs are addresses of resources available on the Web. The first part
is the protocol, followed by the domain name. Moving from one
site to another is called surfing.
Protocol - http://
Domain name - www.umr.edu Web Portals
Web portals are sites that provide a variety of services. Horizontal
portals appeal to mass audiences, ex. "www.aol.com" and vertical portals
appeal to special interest groups, ex. "www.cbs.sportsline.com", etc.
WEB PAGES
Web pages are created in HTML (Hyper Text Markup Language). Browsers
interpret HTML commands to display Web pages. The first page at a Web site
is its HOME PAGE. Pages often have connections or HYPERLINKS to other
documents that contain related information. Applets and Java
JAVA is a programming language for creating special programs called
APPLETS. SEARCH TOOLS
Search tools are used to locate information on the Web. There are
two basic types: INDEXES (topics organized by categories) and SEARCH
ENGINES (topics organized like a database). WEB UTILITIES
Web utilities are programs that increase the performance of
browsers. Two categories are: plug-ins and helper applications. Plug-Ins
Plug-Ins are automatically loaded with the browser and are designed
to better experience a Web site's contents. Helper Applications
Helper applications (add-ons) are independent applications that can be
launched from the browser. Four types are:
ORGANIZATIONAL INTERNETS
Many organizations use Internet technologies in their private
networks. These include Intranets, Extranets, and Firewalls. Intranets
Intranets are private networks within an organization that
resemble the Internet. They use browsers, Web sites, and Web pages
that are available only to those within the organization. Extranets
Extranets are similar to intranets, except that extranets connect more
than one organization. Extranets are often used to connect suppliers and
producers. Firewalls
A firewall is a security system to protect against external threats.
It consists of both hardware and software. All communications into and
out of an organization pass through a special security computer called a
PROXY SERVER. This computer is a gate keeper. All communications between
the organization's internal networks and outside world must pass through
it. By evaluating the source and the content of each communication, the
proxy server decides whether it is safe to let a particular message or
file pass into or out of the organization's network. Speak of
censorship!
THANKS FOR STOPPING BY !
TAKE CARE !