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
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The World Wide WebWhat are the parts of a URL?
protocol domain name path
http://www.nationalgeographic.com/travel/index.html