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Creating a for loop

From: Foundations of Programming: Fundamentals

Video: Creating a for loop

The while loop is the classic loop in C- based languages, but after you've looked at a few you'll realize that a pattern begins to emerge. That you always have to deal with the same elements. Regardless of what code you put in your loop, whether that's one line or a hundred of them, you're dealing with setting up an index to keep track of the loop and you have to do that outside of the loop itself. Then you're going to be checking the condition and then you have to make sure that you're incrementing the index inside the loop, but at the end of it.

Creating a for loop

The while loop is the classic loop in C- based languages, but after you've looked at a few you'll realize that a pattern begins to emerge. That you always have to deal with the same elements. Regardless of what code you put in your loop, whether that's one line or a hundred of them, you're dealing with setting up an index to keep track of the loop and you have to do that outside of the loop itself. Then you're going to be checking the condition and then you have to make sure that you're incrementing the index inside the loop, but at the end of it.

So you always have these three pieces going on to have a successful loop. And this is such a common model. There is actually a statement that brings all these pieces together and that's called a for loop. It's the for statement. It's still follows that same basic if statement format. We've got the word for, we've got the opening and closing parentheses, we got the opening and closing curly braces, but there seems to be an awful lot going on inside these parentheses. Really what we have is the same three pieces that we use in any loop.

We've got the section that sets up the index, we've got the section that checks the condition, and then we've got the section that increments the index, and these three parts are separated with two semicolons. The first time we hit this loop we'll create a variable called i, set it equal to 1, then we'll check to see if it's less than 10, it is, we will jump into the loop, we'll execute all the lines in the body of the loop. when we hit the closing curly brace we'll increment the index, we'll check the condition again, and we'll keep on looping until that condition is no longer true.

The great thing about this is it's really readable. Everything about the loop is right there at the top. You don't have to look outside the loop to find the index being set up nor do you have to scan inside the loop for the increment to make sure that's in the right place. So it's a very clear and straightforward way of setting up a loop. You'll probably find this is more common in any code that you'll find online or in books. And you will find that while loops and for loops will take care of most of the manual looping that you ever need to write. And these are the same across all C-based languages.

Now there is one more loop I'm going to explain, you won't see this an awful lot, but you will run into it from time to time. It's the do or do/while statement. The difference between this and the classic while is we actually move the condition to the end of the block. The format usually looks a little weird because it doesn't match anything that we've seen before, but we still have the same elements in place. I'm setting up an index, var a = 1, then I have the keyword do. I open up the blocks, we've got our code, I've got the incrementer of a++, but the condition that I'm checking is right at the end, while a < 10.

Unlike the while statement we actually do need a semicolon at the end of the do/while statement. Now the really big difference with this format is that the block and whatever is in it will always be executed once before the condition is even looked out. So even if this condition was false, if a started off at 1000, we would execute the code in the block before we check the condition. That may or may not be what you want. So while you will see this from time to time, while loops are much more common than do/while loops.

In most loops you'd expect to check the condition before you enter the loop and it's much more readable to have the condition at the top of the loop as with the while or with a for than at the bottom, which is where you see it when you got a do/while.

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This video is part of

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Foundations of Programming: Fundamentals

61 video lessons · 88805 viewers

Simon Allardice
Author

 
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  1. 4m 15s
    1. Welcome
      1m 17s
    2. Making the most of this course
      2m 8s
    3. Using the exercise files
      50s
  2. 22m 11s
    1. What is programming?
      5m 45s
    2. What is a programming language?
      4m 48s
    3. Writing source code
      5m 34s
    4. Compiled and interpreted languages
      6m 4s
  3. 16m 29s
    1. Why JavaScript?
      4m 45s
    2. Creating your first program in JavaScript
      6m 54s
    3. Requesting input
      4m 50s
  4. 31m 38s
    1. Introduction to variables and data types
      5m 16s
    2. Understanding strong, weak, and duck-typed languages
      3m 51s
    3. Working with numbers
      5m 4s
    4. Using characters and strings
      4m 5s
    5. Working with operators
      4m 47s
    6. Properly using white space
      6m 46s
    7. Adding comments to code for human understanding
      1m 49s
  5. 24m 48s
    1. Building with the if statement
      7m 35s
    2. Working with complex conditions
      4m 9s
    3. Setting comparison operators
      6m 59s
    4. Using the switch statement
      6m 5s
  6. 17m 54s
    1. Breaking your code apart
      4m 1s
    2. Creating and calling functions
      2m 56s
    3. Setting parameters and arguments
      6m 7s
    4. Understanding variable scope
      2m 23s
    5. Splitting code into different files
      2m 27s
  7. 13m 31s
    1. Introduction to iteration
      4m 28s
    2. Writing a while statement
      5m 24s
    3. Creating a for loop
      3m 39s
  8. 19m 28s
    1. Cleaning up with string concatenation
      4m 30s
    2. Finding patterns in strings
      8m 3s
    3. Introduction to regular expressions
      6m 55s
  9. 19m 58s
    1. Working with arrays
      5m 46s
    2. Array behavior
      5m 29s
    3. Iterating through collections
      5m 18s
    4. Collections in other languages
      3m 25s
  10. 10m 50s
    1. Programming style
      5m 55s
    2. Writing pseudocode
      4m 55s
  11. 25m 55s
    1. Input/output and persistence
      3m 6s
    2. Reading and writing from the DOM
      8m 11s
    3. Event driven programming
      7m 47s
    4. Introduction to file I/O
      6m 51s
  12. 24m 25s
    1. Introduction to debugging
      5m 57s
    2. Tracing through a section of code
      7m 5s
    3. Understanding error messages
      3m 21s
    4. Using debuggers
      8m 2s
  13. 14m 16s
    1. Introduction to object-oriented languages
      5m 18s
    2. Using classes and objects
      6m 28s
    3. Reviewing object-oriented languages
      2m 30s
  14. 11m 14s
    1. Memory management across languages
      5m 11s
    2. Introduction to algorithms
      4m 2s
    3. Introduction to multithreading
      2m 1s
  15. 29m 20s
    1. Introduction to languages
      1m 42s
    2. C-based languages
      4m 40s
    3. The Java world
      3m 13s
    4. .NET languages: C# and Visual Basic .NET
      6m 17s
    5. Ruby
      3m 4s
    6. Python
      2m 56s
    7. Objective-C
      4m 3s
    8. Libraries and frameworks
      3m 25s
  16. 1m 2s
    1. Where to go from here
      1m 2s

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