Difference between revisions of "Loops"

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==An Introduction==
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{{1010Chapter|ChapterNum=5
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A loop is a control structure that repeatedly executes a sequence of steps for as long as a [[test condition]] evaluates to true. What does iterate mean?
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|Picture=Wiki_loops03.jpg
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|Introduction=Until now all your programs have been working from top to bottom. Imagine if you were to write a game to guess a secret number from 1 to 100. The entire program would consist of one hundred [[Control Structures#The If Statement|if statements]] to account for each turn to check and see if the number chosen is correct; a situation like this is where a loop will come in to play and reduce those one hundred statements into one.
  
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(Another definition less informal?)
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A loop is a [[Control Structures|control structure]] that allows you to repeat the same sequence of code as long as a given [[test condition]] evaluates to true. Remember that the test condition uses [[Java Fundamentals#Operators|operators]]. Every passage through this sequence of code is called an ''iteration''.  If you repeat the same sequence of code 20 times, then you have performed 20 iterations.
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A loop is a control structure that allows you to repeat the same sequence of code for any given time.
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Until now all your programs have been working from top to bottom. Imagine if you were to write a game to guess a secret number from 1 to 100. The entire program would consist of one hundred if statements to account for each turn to check and see if the number chosen is correct.
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==Types of Loops==
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*[[While Loops|while]]
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*[[for]]                            -Roger
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*[[nested loops]]                  -Roger
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==[[Test_condition|Test Condition]]==
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Loops use the test condition to decide whether or not to enter the body of the loop.
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|Body=
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==[[Looping]]==
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==[[While Loops]]==
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==[[Do-While Loops]]==
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==[[For Loops]]==
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==[[Nested Loops]]==
 
==[[Scope]]==
 
==[[Scope]]==
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Everything within the body of the loop is considered to be in the scope of the loop.  In the case of a for loop, any variable declared in the inializer is considered to be within the scope of the loop.  Declaring a variable within the variable within the scope of a loop is highly discouraged.  This variable would be difined again everything time the loop iterates, causing a significant waste of memory.
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==[[Infinite Loops]]==
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==[[Multiple Control Statements]]==
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==[[Running Totals and Sentinel Values]]==
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==[[Loop Review Questions and Exercises|Review Questions and Exercises]]==
  
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==Infinite Loops==
 
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An infinite loop is any loop that continues to repeat forever.  There are situations where this is useful, but if you didn't intentionally program it in, then it causes a fatal error for your program.  These occur if the test condition in your loop will never be false.  Here are a few examples of infinite loops:
 
  
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<pre>
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|PChapterNum=4
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while(true) //always true
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|PChapterLink=[[Control Structures]]
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{
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|NChapterNum=6
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}
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|NChapterLink=[[User Defined Methods]]
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------------------------------------------------
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}}
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for(int i = 0; i < 20; i++) //counter reset to 0 every time
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{
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    i = 0;
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}
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------------------------------------------------
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for(int i = 0; i < 5e9; i++) //integers can't be as big as 5e9(5*10^9), so i will overflow to negative
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{
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}
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</pre>
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==[[Additional Information]]==
 
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*[[Additional Information#Multiple Control Statments|Multiple Control Statements]]
 
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*[[Additional Information#Do-While Loops|The Evil Do-While Loop]]
 
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*[[Additional Information#Running Totals and Sentinel Values|Running Totals and Sentinel Values]]
 
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==[[Loop Review Questions and Exercises|Review Questions and Exercises]]==
 
  
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Here you will find some Review Questions and Exercises to help you understand and and learn to use loops.
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{{Category:COMP 1010}}

Latest revision as of 21:38, 8 December 2011


Wiki 1010 Table of Contents

Wiki loops03.jpg

Chapter 5

Until now all your programs have been working from top to bottom. Imagine if you were to write a game to guess a secret number from 1 to 100. The entire program would consist of one hundred if statements to account for each turn to check and see if the number chosen is correct; a situation like this is where a loop will come in to play and reduce those one hundred statements into one.

A loop is a control structure that allows you to repeat the same sequence of code as long as a given test condition evaluates to true. Remember that the test condition uses operators. Every passage through this sequence of code is called an iteration. If you repeat the same sequence of code 20 times, then you have performed 20 iterations.

  Write a Program a Day Case Studies

Looping

While Loops

Do-While Loops

For Loops

Nested Loops

Scope

Infinite Loops

Multiple Control Statements

Running Totals and Sentinel Values

Review Questions and Exercises



Chapter 4: Control Structures Table of Contents Chapter 6: User Defined Methods



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