Internet Review

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Internet Review

• CS101A1
• April 30, 2002

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Internet Review
What does robustness mean with respect to a
network?
Resilience to disruptions or faults.
Name two reasons the Internet is considered
robust?
Packets
Routing multiple paths between any two nodes
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Gateway
What is a router?
A network device that connects two or more
networks
What is a gateway?
A router that connects different networks, often
a LAN and the Internet
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Network Layers
Name and describe the five layers of a network
connection
Application Layer
Transport Control Protocol (TCP) Layer
Internet Protocol (IP) layer
Local Access Network (LAN) Protocol
Physical layer
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Layers
Name three reasons for using layers
Modularity (development and configuration)
Efficiency (multitasking)
Reliability
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HTML
What is a tag (and how is it formatted)?
ltcentergt
Most tags come in pairs (T or F)?
True
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How does PHP work?
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PHP
What does PHP add to web pages?
The ability to change the content of a web page
based upon input and processing also, the
ability to store information and execute commands
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PHP-Input
Name two input sources for PHP
(1) Web-page visitors (2) The system
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Programming Languages
What is a programming language?
A human-readable, text-based language for telling
a computer to do something
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PL Categories
Describe the 4 types of Programming Languages
Functional
Imperative
Declarative
Object-Oriented
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Source Code
What is source code?
Text file written in a computer language
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Translating Source Code
Describe two devices for translating source code
into something a computer can understand
Interpreter
Compiler
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Programs
What is a binary?
Executable program you can run
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Programs
Compiled programs are easy to reverse engineer (T
or F)?
False
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Compiling vs. Interpreting
Which uses more overhead when running a program?
Interpreting
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PHP
Is PHP interpreted or compiled, and why?
Interpreted
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Open Source
What is the Open Source Software Movement all
about?
Inclusion of source code along with executable
programs, so users can customize and improve them
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PHP in HTML
What is the PHP tag?
lt?php // your PHP program ?gt
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Echo
Give an example of the echo command
lt?php echo I would like to thank . . . ?gt
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PHP Variables
Name and describe the variable types
Integer (no decimal point)
Float (decimal point)
String (text)
Array (list of one of the other three types)
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Integers vs. Floats
Why are floats less precise than integers?
Integers stored a single number Floats stored as
mantissa and exponent
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Variables in Strings
How would you insert a variable into a string
(e.g., with the echo command)?
lt?php echo Name is name.ltbrgt ?gt
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Flawed Code
Whats wrong with this code? ltphp Name
Judy Echo Name ?gt
lt?php


Name
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What does this do?
a getenv(REMOTE_ADDR) echo a
Prints the visitors IP address
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Whats the result?
a 21 b 7 a / b echo a
3
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Whats the result?
a 6 b a 5 a -2 b / a echo
b
7
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What does this do?
b . a
. is the concatenation operator a is appended to
the end of b b Happy b . Birthday!
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Format of if ... else statement?
if ( a gt 5 ) echo Yea, dude! else
echo No way!
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Rewrite as while statement
for ( i 0 i lt 10 i ) echo i
i 0 while ( i lt 10 ) echo i i
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What will happen here?
a 1 while ( a gt 0 ) echo a
Infinite Loop!
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What do these do?

OR

AND
!
NOT
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Whats the result?
floor( 12.9 )
12
round( 2.1 )
2
ceil( sqrt( 10 ) )
4
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Forms
Describe five form objects
Text field Check box Radio button Pull-down
menu Button
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Forms and PHP
How do you use a form to get information to a PHP
script?
ltform valuenamegt becomes name ltform
actiondoit.phpgt