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IT441 Network Services Administration. Prof. Alfred J Bird, Ph.D., NBCT abird@cs.umb.edu http://it441-f12.wikispaces.umb.edu/ Office – Wheatly 2nd floor 096-03 Office Hours – MW 3:00PM to 4:00PM. Comment Blocks. Perl normally treats lines beginning with a # as a comment.

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IT441 Network Services Administration

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IT441Network Services Administration

Prof. Alfred J Bird, Ph.D., NBCT

abird@cs.umb.edu

http://it441-f12.wikispaces.umb.edu/

Office – Wheatly 2nd floor 096-03

Office Hours – MW 3:00PM to 4:00PM


Comment Blocks

  • Perl normally treats lines beginning with a # as a comment.

  • Get in the habit of including comments with your code.

  • Put a comment block at the beginning of your code which includes your name, the name of the module, date written and the purpose of the code.


Alternative String Delimiters

  • q// single quoted string

  • qq// double quoted string

  • In qq// the // can be replaced with any other non-alphanumeric character provided you use the same character on both ends of the string


Operators on Strings and Numbers

  • $a = “123”

  • $b = “456”

  • What do we get if we write this line of code,

    • print $a + $b;

  • How about this line of code,

    • print $a . $b;


  • Math Operators

    • ** Exponentiation

    • -Unitary Negation

    • * Multiplication

    • /Division

    • %Modulo (Remainder)

    • +Addition

    • -Subtraction


    What is an Algorithm

    • In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning. In simple words an algorithm is a step-by-step procedure for calculations.


    File Operations

    • To use a file we need to attach a filehandle to it.

    • We do this using the open statement.

    • A simple example:

      • open (OUT1, “>testoutout.txt”);

    • If we open it we want to close it after we are done:

      • close (OUT1);

    • By convention a filehandle is codded in all capital letters


    A better way

    • We want to know for sure that we were successful opening the file so we include a test:

    • open (OUT1, “>>test.txt”) or die $!;


    Using a filehandle

    • To use a filehandle you wrap it in angle brackets.

    • print <OUT1> “Hello World!\n”;

    • chomp ($in = <IN1>);


    I/O Redirectors

    • Remember what the redirectors do:

      • >

      • >>

      • <


    Three problems to code

    • Calculate the first 50 prime numbers and write them to an output file.

    • Calculate the first 40 members of the Fibonacci Series and write them to an output file.

    • Read the two output files and print them to the screen.


    Next Time

    • Read pages 179 to 185 in the Perl book

    • Complete the four programs


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