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Introduction to Perl Programming: Comments, Algorithms, and File Operations

This course provided by Prof. Alfred J. Bird covers foundational topics in Perl programming, including best practices for writing comments, utilizing alternative string delimiters, and understanding math and string operators. Students will learn about algorithms as step-by-step instructions for problem solving, file operations for reading and writing data, and conducting input/output tasks. By the end of the course, participants will be equipped to implement code for practical problems like generating prime numbers and Fibonacci sequences while effectively using file handles.

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Introduction to Perl Programming: Comments, Algorithms, and File Operations

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  1. 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

  2. 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.

  3. 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

  4. 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;

  5. Math Operators • ** Exponentiation • - Unitary Negation • * Multiplication • / Division • % Modulo (Remainder) • + Addition • - Subtraction

  6. 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.

  7. 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

  8. 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 $!;

  9. Using a filehandle • To use a filehandle you wrap it in angle brackets. • print <OUT1> “Hello World!\n”; • chomp ($in = <IN1>);

  10. I/O Redirectors • Remember what the redirectors do: • > • >> • <

  11. 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.

  12. Next Time • Read pages 179 to 185 in the Perl book • Complete the four programs

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