pg. 16 - 24

1) The CPU
- uses main memory to perform all the basic processing in a comp.
- consists of 3 components
1) Control unit: handles the processing steps
2) Registers: small amounts of storage space in the CPU itself.
3) Arithmetic/logic unit: does calculations and makes decisions.

- program counter: holds the address of the next instructions to be executed

2) von Neumann architecture
- the idea of storing program instructions and data together in main memory. (first advanced in 1945)

- fetch-decode-execute cycle.
1) Fetch an instruction from main memory
2) Decode the instruction and increment program counter.
3) Execute the instructions

3) Parts on main circuit board
- the CPU is on a chip called a microprocessor
- System clock: sends out an electronic pulse at regular intervals, so that everything on CPU happens on schedule.
- The clock speed tells you how fast the CPU reads instructions. (clock speed: rate of pulses)

4) Networks
- two or more computers connected together so they can exchange info.
- each computer on the network is a file server.

5) Network Connections
- point-to-point connection: two computers close to each other.
- In this connection, every computer is connected to a wire to every other computer in the network.

- In a network each computer has its own network address. (like the address in main memory but for computers!)

- Sharing a communication line is less expensive and makes adding new computers to the network easier.
- but a shared line means delays.
- the computers on the network cannot use the line at the same time. They have to take turns (busy).

- too improve network delay, we use packets (dividing the large messages into small pieces)
- The individual packets are sent across the network mixed up with pieces of other messages sent by other users.
- Packets are put back together to make original message.
*** This “packets” method is faster than waiting in line.

6) Local-area networks (LAN) & WAN
- designed to span short distances and connect a small number of computers.
- Wide-area network (WAN) connects two or more LANs, often across local distances.

7) The Internet
- During the 1970s, a US gov’t organization called the Advanced Research Projects Agency (ARPA) funder project to explore network technology.

- Result was APRANET, a WAN that eventually became known as the Internet.
- The internet is a network of networks
- the term ”internet” comes from the word internetworking - connecting many smaller networks together.

- In 1983, there was only 600 computers connected to internet, by 2000 there was over 2 million!

- a protocol is a set of rules about how two things communicate.
- the software that controls the movement of messages across the Internet must follow a set of protocols called TCP/IP (Transmission Control Protocol/ Internet Protocol)
1) IP software defines how info is formatted and transferred.
2) TCP software handles problems such as pieces of info arriving out of order or getting lost.

- IP address: every computer connected to the internet has this to ID itself among all other computers in the internet.
- Internet address: internet name of computer.

- the first part of an Internet address is the local name of a specific computer. The rest is the domain name. (there are sub domains also)
- Top-level Domain (TLD) indicates the type of organization to which the computer belongs.
- Domain Name System (DNS): Software that translates the IP address.

8) World Wide Web (WWW)
- based on the ideas of hypertext and hypermedia
- hypertext: first used in 1965 to describe a way to organize info. “jumping for one document to another”
- when graphics, sounds, and animation are mixed in we call this hypermedia.

- Browser: a software tool that loads and formats web documents for viewing
- Mosaic, the first graphical interface browser for the web, released in 1993.
- Some people who developed mosaic went on to discover NETSCAPE (today’s browser)

- Web Server: a computer dedicated to providing access to web documents.
- Many of these docs use HTML (HyperText Markup Language). Java can be embedded.

9) Uniform Resource Locators (URLs)
- Every web document has this.
- URLs contains several pieces of info
1) protocol: which determines the way the browser should communicate.
2) Internet address of the machine on which the document is stored.
3) the third is the file name

http://www.gestalt-llc.com/vision.html.

1) In this URL, the protocol is http, which stands for HyperText Transfer Protocol.
2) The machine referenced is www (a typical reference to a web server), found at domain gestalt-llc.com.
3) Finally, vision.html is a file to be transferred to the browser for viewing.

10) The Internet vs. The World Wide Web
- The term internet and world wide web do no mean the same thing.
- The internet is a network of computers all over the world.
- The Web is a set of software applications that lets us used the internet to view and exchange programs.
- The Web is not a network, it is a software.