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) 2Microsoft Visual C# 2012, Fifth Edition

Using the while Loop (cont’d.) 3Microsoft Visual C# 2012, Fifth Edition

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 4Microsoft Visual C# 2012, Fifth Edition

Using the while Loop (cont’d.) 5Microsoft Visual C# 2012, Fifth Edition

Using the while Loop (cont’d.) 6Microsoft Visual C# 2012, Fifth Edition

Using the while Loop (cont’d.) 7Microsoft Visual C# 2012, Fifth Edition

8 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 9Microsoft Visual C# 2012, Fifth Edition

Using the while Loop (cont’d.) 10Microsoft Visual C# 2012, Fifth Edition

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 11Microsoft Visual C# 2012, Fifth Edition

Using the for Loop (cont’d.) 12Microsoft Visual C# 2012, Fifth Edition

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 13Microsoft Visual C# 2012, Fifth Edition

14Microsoft Visual C# 2012, Fifth Edition Using the do Loop (cont’d.)

15Microsoft Visual C# 2012, Fifth Edition

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 16Microsoft Visual C# 2012, Fifth Edition

Using Nested Loops (cont’d.) 17Microsoft Visual C# 2012, Fifth Edition

18Microsoft Visual C# 2012, Fifth Edition

19 Microsoft Visual C# 2012, Fifth Edition

Accumulating Totals Totals are accumulated – Gathered together and added into a final sum by processing individual records one at a time in a loop 20Microsoft Visual C# 2012, Fifth Edition

Accumulating Totals (cont’d.) 21Microsoft Visual C# 2012, Fifth Edition

Accumulating Totals (cont’d.) 22Microsoft Visual C# 2012, Fifth Edition

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 23Microsoft Visual C# 2012, Fifth Edition

24Microsoft Visual C# 2012, Fifth Edition Looping Issues in GUI Programs (cont’d.)

25Microsoft Visual C# 2012, Fifth Edition Looping Issues in GUI Programs (cont’d.)

26Microsoft Visual C# 2012, Fifth Edition Looping Issues in GUI Programs (cont’d.)

27Microsoft Visual C# 2012, Fifth Edition Looping Issues in GUI Programs (cont’d.)