Coding 101 3

Welcome to Coding 101 - It's the TWiT show that gives YOU the knowledge to live in the wonderful world of the programmer. This week we are taking a look at Xamarin Studio on MacOS X, While Loops, For Loops, and Relational Operators.

Reviewing While Loops and A Mac OSX IDE Option

How do I download and compile my first code on a Mac? Download the C# Compiler from the MonoDevelop website.

• Choose the Xamarin Studio package and download it.
• Click on the Mono + GTK# download link.
• Download the Intel Mac: Runtime or SDK links and install.
• Once all three programs are installed, open the Xamarin Studio application.
• From the main page, choose New, C#, Console Application.
• Start writing your code!

My While Loop looks like this:

• int counter = 368;
  • This will give me an integer variable called counter, which equals 368.
• while (counter > 0)
  • This is the start of my while loop, with counter being greater than zero.
• Console.WriteLine(counter);
  • The loop states that every time my counter is greater than zero, to write out the counter number on my output.
• counter = counter - 5;
  • This changes the counter variable. So each time my while loop restarts, it's going to subtract 5 from the total, until the counter is no longer greater than zero.

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Ivory Tower!

Relational Operators

Remember the while loop? The loop has a "()" section that determines if the loop will run. That section is called the "conditon" - as long as the condition is TRUE, the loop will run. Those conditions use "Relationtional Operators"

• Code elements that let you compare two operators against a relationship.

Those relational operators are:

• "<" Less Than
• ">" Greater Than
• ">=" Greater Than or Equal to
• "<=" Less that or Equal To
• "==" Equal To
• "!=" Not Equal To

(3==3) is true, (2<1) is false, (71>=23) is true. Those would all work within that section, h However, those conditions are ALWAYS true or ALWAYS false. That's useless in a loop because the loop would either never terminate, or it would never run. That's why we use variable within the condition, so that we can change the "trueness" or "falseness" of a condition.

for loop

The "for loop" is a "pretest" loop. Which means that, like the while loop, it will test the expression within the condition before ever running the code within the loop. (There IS a technique to make it a post-test loop, but we'll get to that later.) Unlike the "while loop", which requires you to separately initialize the counter, create the condition and set the interator (step), every "for loop" defines its own initializer, condition, and iterator.

Example:

for (int counter=5; counter <= 10; counter++) {
  console.write ("The count is currently ");
  console.writeln (counter);
}

The output will be:

The count is currently 5
The count is currently 6
The count is currently 7
The count is currently 8
The count is currently 9
The count is currently 10

1. The for loop will initialize an INT variable named "counter" and assign it the value of "5"
2. The for loop will check the condition of the expression "counter >= 10" -- since we set the value of counter at 5, the condition is true.
3. If the condition is true, the loop will execute
4. the for loop will then perform the "step" -- the increment or decrement that we specify

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• Transcripts: Coding 101 Episode 3 (Transcript)