Programming

Perl


Perl is a scripting language that is supported on all computing platforms (Windows, Unix, Linux, Mac, and mobile devices). It is called a scripting language because it executes immediately without the need for a compile step. This makes writing programs in Perl very fast, but the programmer has to keep track of the variables being used and make sure they are set before they are tested.

The lines that start with a hash (#) are comments and can be placed anywhere in the code to help make it easier to read and understand.

Download software: http://www.perl.org/

Cost: Free

Instructions to setup software: http://learn.perl.org/

Hardware requirements: Any PC or laptop computer

Operating systems supported: Win, Mac OS X, Linux

Difficulty level: 2 out of 5


TRY IT!

1. Install the Perl compiler on your computer or laptop.

2. Open a text editor (notepad, textedit, vi, or your favorite) and copy/paste the following program into a file:


#...initialize looping variable, assume 'yes' as the first answer
$continueYN = "y";

while ($continueYN eq "y")
{
   #...get temperature input from the user
   print "Enter next temperature in degrees Farenheight (F):";

   $degreeF = <STDIN>;
   chomp($degreeF);

   #...convert temperature from F to Celsius
   $degreeC = ($degreeF - 32) * 5 / 9;

   print "Temperature in degrees C is: ".$degreeC."\n";

   #...check for temperature below freezing..
   if ($degreeC < 0)
   {
      print "Pack long underwear!\n";
   }

   #...check for it being a hot day...
   if ($degreeF > 100)
   {
      print "Remember to hydrate!\n";
   }

   print "Input another?";

   $continueYN = <STDIN>;
   chomp($continueYN);
}

3. Save it as “test.pl”

4. Open a command window (cmd.exe, or Unix shell) on your computer and navigate the default directory to the place where you stored “test.pl”

5. Run the program with the command “perl test.pl”


TRY THIS

1. Change the messages to have different advice for extreme temperatures.

2. Change the trigger temperatures (hot or cold) to something different.

3. Add another temperature trigger check for very extreme temps.

4. Collect the person’s name before the loop starts (store in a variable) and add this to the output messages.

5. (Advanced) Change the whole program into a currency converter. Input amount in US dollars and convert to Euros.


LEARN MORE

learn.perl.org — This site has many examples and other tutorials.

Perl-tutorial.org -– This hub site has links to many other tutorials and examples.

Cpan.org -– Comprehensive Perl Archive Network. Contains many libraries of pre-written programs that can be downloaded and used in your projects. Animation, graphics, encryption, and network utilities are just a few of the kinds of resources available.

Google.com -– Search for other code and samples.


RESOURCES, TIPS, TRICKS AND HINTS

Scripting languages do not need a compiler, so you can quickly write and test programs by keeping several windows open on your computer. Just keep your working program open in a text editor (like notepad) and have another window open that is running a command line prompt. Then make small changes to the file, save it, and then run it in the other windows. You can grow a simple program into a complex one in this manner.

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  • 1. Safety. Do the following:
      a. Show your counselor your current, up-to-date Cyber Chip.
      b. Discuss first aid and prevention for the types of injuries or illnesses that could occur during programming activities, including repetitive stress injuries and eyestrain.

    2. History. Do the following:
      a. Give a brief history of programming, including at least three milestones related to the advancement or development of programming.
      b. Describe the evolution of programming methods and how they have improved over time.

    3. General knowledge. Do the following:
      a. Create a list of 10 popular programming languages in use today and describe which industry or industries they are primarily used in and why.
      b. Describe three different programmed devices you rely on every day.

    4. Intellectual property. Do the following:
      a. Explain how software patents and copyrights protect a programmer.
      b. Describe the difference between licensing and owning software.
      c. Describe the differences between freeware, open source, and commercial software, and why it is important to respect the terms of use of each.

    5. Projects. Do the following:
      a. With your counselor’s approval, choose a sample program. Then, as a minimum, modify the code or add a function or subprogram to it. Debug and demonstrate the modified program to your counselor.
      b. With your counselor’s approval, choose a second programming language and development environment, different from those used for requirement 5a and in a different industry from 5a. Then write, debug, and demonstrate a functioning program to your counselor, using that language and environment.
      c. With your counselor’s approval, choose a third programming language and development environment, different from those used for requirements 5a and 5b and in a different industry from 5a or 5b. Then write, debug, and demonstrate a functioning program to your counselor, using that language and environment.
      d. Explain how the programs you wrote for requirements 5a, 5b, and 5c process inputs, how they make decisions based on those inputs, and how they provide outputs based on the decision making.

    6. Careers. Find out about three career opportunities in programming. Pick one and find out the education, training, and experience required. Discuss this with your counselor and explain why this career might be of interest to you.

  • Earning the Cyber Chip can help you learn how to stay safe while you are online and using social networks or the latest electronic gadgets.

    Topics include cell phone use, texting, blogging, gaming, cyberbullying, and identity theft. Find out more about the Cyber Chip at www.scouting.org/cyberchip.