1. Programming Basics
Web Programming

2. Programming Intro What is programming? Why do we need it?
breaking down tasks into small steps e. g. count the words in “program=set of instructions to perform a task.”
Why do we need it?
Computer is not “intelligent”.
Computer can perform multiple tasks fast and reliably.
How do we do it?
Learn to think logically and detail-oriented.
Learn the syntax of a specific programming language.
Practice (code, execute, debug, repeat).
Design & implement systems.
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3. Perl Intro: What is Perl?
What is Perl? (Practical Extraction and Report Language)
an interpreted programming language optimized for string manipulation, I/O, and system tasks
Interpreted (vs. compiled) programming language
code & execute (vs. code-compile-execute)
translated to machine code at runtime (vs. compile time)
faster to program/debug/modify
slower execution time since “intepreted” at runtime
simpler (easier to learn, but less powerful)
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4. Perl Intro: Why Perl? Why Perl? relatively easy to learn
well-suited for CGI tasks
CGI tasks (translation btw. user and server) involve string manipulation.
Advantages (speed, power) of compiled languages are negligible in CGI environment.
CGI tasks usually do not require heavy computations.
Network bandwidth is the bottleneck in the Web.
portable: runs on most (Web server) O/S
WIRED article: “Perl Simplifies the Labyrinth That is Programming Language”
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5. Perl Basics Basic Syntax
free form
spaces, indentations have no meaning to Perl interpreter.
program statements end in ;
comments start with #, end at the line break.
Running a Perl program (from unix command line)
method 1
perl [-switch] program_name
method 2
put #!/usr/bin/perl at the first line in the script.
set file permission to be executable.
Chmod 755 program_name
program_name
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6. Example #1 # my first program print “I program, therefore I am.”;
‘print’ sends to standard (screen) output.
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7. Example #2 #!/usr/bin/perl # using a variable $name= “Sam”;
print “I am $name. Who are you?\n”;
$ denotes a (scalar) variable.
“$name” resolves the variable.
‘\n’ is a newline character.
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8. Example #3 #!/usr/bin/perl # interacting w/ user $my_name= “Sam”;
print “I am $my_name. Who are you?”;
$your_name= <STDIN>;
print “$your_name, it’s nice to meet you.”;
<STDIN> reads from standard (keyboard) input.
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9. Example #4 #!/usr/bin/perl # paying attention to user interface
$my_name= “Sam”;
print “\nI am $my_name. Who are you?\n ”;
$your_name= <STDIN>;
chomp $your_name;
print “$your_name, it’s nice to meet you.\n\n”;
‘chomp’ deletes the newline character.
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10. Example #5
#!/usr/bin/perl # working with numbers $a=1; $b= 2+2; $c= 2*2; $d= $b/$c; print “$a = $d”; print “\n”;
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