The System UnitThe System UnitWhat is the motherboard?

Also called the system board Main circuit board in the

system unit Contains many

electronic components

Central Processing UnitCentral Processing UnitWhat are the components of the central processing unit (CPU )?

CPU

Arithmetic/Logic Unit

(ALU)

Control Unit

Central Processing UnitCentral Processing Unit

A student enters a math problem into the memory of the computer

Step 1: The control unit fetches the math problem from memoryStep 2: The control unit decodes the math problem and sends it to the ALU

Step 3: The ALU executes the math problemStep 4: The results of the math problem are stored in memory

The result in memory displays on the screen of the monitor

What is a machine cycle?Together the four operations of the CPU comprise a

machine cycle

Central Processing UnitCentral Processing Unit

How is the speed of the CPU measured? According to

how many millions of instructions per second (MIPS) it can process

Data RepresentationData RepresentationWhat is the binary system?

Binary Digit (bit)

Electronic Charge

Electronic State

A number system that has just two unique digits, 0 and 1• A single digit is called a bit (binary digit)

• A bit is the smallest unit of data the computer can represent

• By itself a bit is not very informative

The two digits represent the two off and on states

Data RepresentationData RepresentationWhat is a byte?

8-bit byte for the number 3

8-bit byte for the number 5

8-bit byte for the capital letter T

Eight bits are grouped together to form a byte 0s and 1s in each byte are used to represent

individual characters such as letters of the alphabet, numbers, and punctuation

Data RepresentationData Representation

American Standard Code for Information Interchange (ASCII)

MemoryMemory

• Bytes are the basic storage unit in memory

• Each byte is stored at a specific location in memory called an address

How are bytes stored?

Each address has a unique identifying number, like the seats on an airplane

seat C22 seat B22 seat A22

Each address can hold only a single byte

Each address can be full or empty

MemoryMemoryHow is memory measured? Size of memory is measured by the number of

bytes available

• Kilobyte - 1,024 bytes

• Megabyte - one million bytes

Storage (hard disk)

RAM

Step 3: When you quit Word, RAM may be used to store another program or data. The program is removed from the screen and the operating system’s user interface redisplays.

Step 1: When your computer is running, certain operating system files are in RAM. Shown here is the operating system’s user interface.

Step 2: When you start a word processing program such as Word, the program loads into RAM from a hard disk. As you create a document, it is in RAM and displays on your screen.

Step 4: When you start a spreadsheet program such as Excel, the program loads into RAM from a hard disk. As you create a spreadsheet, it is in RAM and displays on your screen.

MemoryMemoryHow are applications transferred in and out of RAM?

Step 5: When you quit Excel, RAM may be used to store another program or data. Excel is removed from your screen and the operating system’s user interface redisplays.

Mobile ComputersMobile Computers

An IrDA port allows the handheld computer to communicate wirelessly with other computers or devices

Handheld computers also can rest in a cradle, so you can transfer data to your desktop computer

How is data transferred from a handheld computer? IrDA port

cradle

Goal:

To function even if part of the network

were disabled or destroyed

Became functional

in September

1969

Goal:To allow scientists at different locations to

share information and work together

on military and scientific projects

History of the InternetHow did the Internet originate?

ARPANET

Networking project by Pentagon’s

Advanced Research Projects Agency

(ARPA)

p. 2.3

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History of the InternetWhat is a host node?• Also called a host• Any computer that

directly connects to a network

• Often stores and transfers data and messages

• Provides network connections for other computers

• Four original nodes on ARPANET

University of California at Los Angeles

University of California at

Santa Barbara

University of Utah

Stanford Research Institute

p. 2.4

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Technology TrailblazerTim Berners-Lee• Created the World Wide Web

Director of the World Wide Web Consortium (W3C) at MIT

Click to view Web Linkthen click Tim Berners-Lee

p. 2.4

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How might data travel the Internet using a telephone line connection?

Step 1Step 1Step 2

Step 1Step 2

Step 3

Step 1Step 2

Step 3

Step 4

Regional ISP

Step 1Step 2

Step 3

Step 4

Step 5

Regional ISP

National ISP

Step 1Step 2

Step 3

Step 4

Step 5

Step 6

Regional ISP

National ISP

National ISP

Internet backbone

Step 1Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Regional ISP

Local ISP

National ISP

National ISP

Internet backbone

How the Internet Works

Step 1Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 8

Regional ISP

Local ISP

National ISP

National ISP

Internet backbone

1: You initiate an action to request data from the Internet.

2: A modem converts the digital signals from the computer into analog signals, which are understood by telephone lines.

3: Data (request) travels through telephone lines to a local ISP.

4: Data may pass through one or more routers before reaching its final destination.

5: The regional ISP uses lines, leased from a telephone company, to send data to a national ISP.

6: The national ISP routes data across the country to another national ISP.

7: Data moves from a national ISP to a local ISP and then to a destination server.

8: The server retrieves the requested data and sends it back through the Internet backbone to your computer.

p. 2.7 Fig. 2-3

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How the Internet WorksWhat is an Internet protocol (IP) address?• Number that uniquely identifies each computer or device

connected to the Internet• Four groups of numbers, each separated by a period• Number in each group is between 0 and 255

IP address 199.95.72.10

first part identifies network

last part identifies specific

computer

p. 2.8 Fig. 2-4

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How the Internet WorksWhat is a domain name?• Text version of an IP address• Components are separated by periods• Each domain name represents one or more IP addresses

IP address 199.95.72.10

Domain name www.scsite.com

p. 2.8 Fig. 2-4

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How the Internet WorksWhat is a top-level domain (TLD) abbreviation?

• Identifies the type of organization associated with the domain

• Sometimes called dot com when TLD is com

p. 2.8 Fig. 2-5

Next

The World Wide WebWhat are the parts of a URL?

protocol domain name path

http://www.nationalgeographic.com/travel/index.html