IT441 Network Services Administration

IT441Network Services Administration Prof. Alfred J Bird, Ph.D., NBCT abird@cs.umb.edu http://it441-s14-bird.wikispaces.umb.edu/ Office – McCormick 3rd floor 607 Office Hours – Tuesday and Thursday 4:00PM to 5:15PM

Last Class Programming Challenges • A program to print out a list of the squares and cubes of the numbers from 1 to 20. • A program to ask for a number and test if it is a prime number. • A program to ask for two numbers and print out the sum of the numbers until it is told to stop. • A program to chose a specific action based upon an alpha input.

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 three programs

IT441 Network Services Administration