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Chapter 5:
Looping
Using the while Loop
• Loop
– A structure that allows repeated execution of a block of statements
• Loop body
– A block of statements within a looping structure
• C# types of loops: – while loop
– for loop
– do loop (or do...while loop)
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Using the while Loop (cont’d.)
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Using the while Loop (cont’d.)
• while loop
– Used to execute a body of statements continuously as long as some condition continues to be true
• Infinite loop
– A loop that never ends
• Making a while loop end correctly
– Initialize the loop control variable
– Test the control variable in the while expression
– Alter the value of the control variable in the code block
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Using the while Loop (cont’d.)
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Using the while Loop (cont’d.)
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Using the while Loop (cont’d.)
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Using the while Loop (cont’d.)
Using the while Loop (cont’d.)
• Empty body – A body with no statements in it
• Alter the control variable by:
– Incrementing, or adding to it
– Decrementing, or subtracting from it
• Definite loop or counted loop
– A loop for which the number of iterations is predetermined
• Indefinite loop
– The value of a loop control variable is not altered by arithmetic, but instead is altered by user input
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Using the while Loop (cont’d.)
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Using the for Loop
• for loop
– A shorthand way to create definite loops
• Sections of the loop
– Control variable initialization
– Control variable testing
– Control variable updating
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Using the for Loop (cont’d.)
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Using the do Loop
• do loop
– Checks at the “bottom” of the loop after one repetition has occurred
– Convenient when you know you want to perform some task at least one time
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Using the do Loop (cont’d.)
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Using Nested Loops
• When loops are nested, each pair contains an inner loop and an outer loop
– The inner loop must be entirely contained within the outer loop
– Loops can never overlap
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Using Nested Loops (cont’d.)
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Accumulating Totals
• Totals are accumulated
– Gathered together and added into a final sum by processing individual records one at a time in a loop
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Accumulating Totals (cont’d.)
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Accumulating Totals (cont’d.)
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Looping Issues in GUI Programs
• Using a loop within a method in a GUI application is no different from using one in a console application
• Event-driven programs sometimes require fewer coded loops
– Some events are determined by the user’s actions when the program is running, rather than by the programmer’s coding
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Looping Issues in GUI Programs (cont’d.)
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Looping Issues in GUI Programs (cont’d.)
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Looping Issues in GUI Programs (cont’d.)
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Looping Issues in GUI Programs (cont’d.)