Data hierarchy (Figure 6.1)bit - smallest piece of data

byte – character

field - group of bytes

record - related fields

file - related records

database - related files and data about them

File Processing vs Database

• Data independence

• Data redundancy

• Data consistency

• Data sharing

Database Management Systems

• A software that organizes data for easy retrieval and access

3 components (relational):

• Data definition language (tables)

• Data manipulation language (SQL)

• Data dictionary (fields, field types, keys …)

Telecommunications

• Communications by electronic means over some distance

• Telecommunication systems functions – transmits information

– establishes a path/connection between the sender and receiver

– directs messages along the most efficient paths

– ensures messages reaching the right receiver

– edits data by performing error checking and reformatting

– converts messages from one device to another

– controls information flow

Figure 7.5 Five Components of a Telecommunication System• Computer (process information)• Software (network, access, transmission, error, and security control)• Processor (modems, mulitplexer, …)• Channel (fiber-optic, cable, satellite, …)• Input/Output Devices (send/receive data)

Figure 7.2 MOdulation/DEModulation

Networks

• Ways of organizing telecommunications components:– Topology

• Star

• Bus

• Ring

– Scope• Private branch exchange (PBX), e.g., UK’s phone systems

• Local area networks (LAN), e.g., BEIC lab

• Wide area networks (WAN), e.g., UK’s web

• Value-added networks (VAN), e.g., AOL

• The Internet

Figure 7.8 A Local Area Network (LAN)

History of the Internet• ARPANET (1969-1990)

– the U.S. Defense Department’s Advanced Research Projects Agency (ARPA) to facilitate data sharing

• NSFNET (1986-1995)

– the National Science Foundation’s (NSF) national network for university communications

• Internet (1990)

– Business use of the Internet promotes the development of World Wide Web

World Wide Web

• A system and a set of standards for storing, retrieving, formatting, and displaying information in a networked environment using graphical user interfaces and dynamic links to documents

Web Terms• HTML (Hypertext Markup Language) is a

standard language for Web site programming so that navigation tools are able to display the Web site as it was designed without the need to coordinate software packages. Simple html can be created directly through word processing and presentation packages. Special Web authoring tools exist to create more elaborate pages.

Web Terms

• Uniform Resource Locator is the address of a specific resource on the Internet

• A Web browser is a tool for navigation and display of sites. There are many Web browsers with Mosaic being the first.

• Search engines help users locate information on specific topics

• Standards– Transmission Control Protocol/Internet

Protocol (TCP/IP), DOE, 1972:• Layered protocol (Link, Network, Transport,

Application) that sends data as packets

– Integrated Services Digital Network (ISDN)• Standards for transmitting voice data, and video

over phone lines

Applications

• E-mail, voice mail, fax

• Teleconferencing, videoconferencing• Electronic data interchange: direct electronic

exchange of business transaction documents between two separate organizations

• Electronic commerce