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Computer Science: A Structured Programming Approach Using C1 Objectives ❏ To understand basic loop concepts: ■ pretest loops and post-test loops ■ loop.

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Presentation on theme: "Computer Science: A Structured Programming Approach Using C1 Objectives ❏ To understand basic loop concepts: ■ pretest loops and post-test loops ■ loop."— Presentation transcript:

1 Computer Science: A Structured Programming Approach Using C1 Objectives ❏ To understand basic loop concepts: ■ pretest loops and post-test loops ■ loop initialization and updating ■ event and counter controlled loops ❏ To understand and be able to select the best loop construct for a given problem. ❏ To write programs that use the while, for, or do... while statements. ❏ To understand the basic concepts and usage of recursion algorithms. ❏ To understand and be able to determine the efficiency of an algorithm through an analysis of its looping constructs. Chapter 6 Chapter 6 Repetition Repetition

2 Computer Science: A Structured Programming Approach Using C2 6-1 Concept of a loop The real power of computers is in their ability to repeat an operation or a series of operations many times. This repetition, called looping, is one of the basic structured programming concepts. Each loop must have an expression that determines if the loop is done. If it is not done, the loop repeats one more time; if it is done, the loop terminates.

3 Computer Science: A Structured Programming Approach Using C3 FIGURE 6-1 Concept of a Loop

4 Computer Science: A Structured Programming Approach Using C4 6-2 Pretest and Post-test Loops We need to test for the end of a loop, but where should we check it—before or after each iteration? We can have either a pre- or a post-test terminating condition. In a pretest loop, the condition is checked at the beginning of each iteration. In a post-test loop, the condition is checked at the end of each iteration.

5 Computer Science: A Structured Programming Approach Using C5 Pretest Loop In each iteration, the control expression is tested first. If it is true, the loop continues; otherwise, the loop is terminated. Post-test Loop In each iteration, the loop action(s) are executed. Then the control expression is tested. If it is true, a new iteration is started; otherwise, the loop terminates. Note

6 Computer Science: A Structured Programming Approach Using C6 FIGURE 6-2 Pretest and Post-test Loops

7 Computer Science: A Structured Programming Approach Using C7 FIGURE 6-3 Two Different Strategies for Doing Exercises

8 Computer Science: A Structured Programming Approach Using C8 FIGURE 6-4 Minimum Number of Iterations in Two Loops

9 Computer Science: A Structured Programming Approach Using C9 6-3 Initialization and Updating In addition to the loop control expression, two other processes, initialization and updating, are associated with almost all loops. Loop Initialization Loop Update Topics discussed in this section:

10 Computer Science: A Structured Programming Approach Using C10 FIGURE 6-5 Loop Initialization and Updating

11 Computer Science: A Structured Programming Approach Using C11 FIGURE 6-6 Initialization and Updating for Exercise

12 Computer Science: A Structured Programming Approach Using C12 6-4 Event- and Counter-Controlled Loops All the possible expressions that can be used in a loop limit test can be summarized into two general categories: event-controlled loops and counter-controlled loops. Event-Controlled Loops Counter-Controlled Loops Loop Comparison Topics discussed in this section: 6-4 Event- and Counter-Control

13 Computer Science: A Structured Programming Approach Using C13 FIGURE 6-7 Event-controlled Loop Concept

14 Computer Science: A Structured Programming Approach Using C14 FIGURE 6-8 Counter-controlled Loop Concept

15 Computer Science: A Structured Programming Approach Using C15 Table 6-1Loop Comparisons

16 Computer Science: A Structured Programming Approach Using C16 6-5 Loops in C C has three loop statements: the while, the for, and the do…while. The first two are pretest loops, and the the third is a post-test loop. We can use all of them for event-controlled and counter-controlled loops. The while Loop The for Loop The do…while Loop The Comma Expression Topics discussed in this section:

17 Computer Science: A Structured Programming Approach Using C17 FIGURE 6-9 C Loop Constructs

18 Computer Science: A Structured Programming Approach Using C18 FIGURE 6-10 The while Statement

19 Computer Science: A Structured Programming Approach Using C19 FIGURE 6-11 Compound while Statement

20 Computer Science: A Structured Programming Approach Using C20 PROGRAM 6-1Process-control System Example

21 Computer Science: A Structured Programming Approach Using C21 PROGRAM 6-2A while Loop to Print Numbers

22 Computer Science: A Structured Programming Approach Using C22 PROGRAM 6-2A while Loop to Print Numbers

23 Computer Science: A Structured Programming Approach Using C23 PROGRAM 6-3Adding a List of Numbers

24 Computer Science: A Structured Programming Approach Using C24 PROGRAM 6-3Adding a List of Numbers

25 Computer Science: A Structured Programming Approach Using C25 FIGURE 6-12 for Statement

26 Computer Science: A Structured Programming Approach Using C26 FIGURE 6-13 Compound for Statement

27 Computer Science: A Structured Programming Approach Using C27 A for loop is used when a loop is to be executed a known number of times. We can do the same thing with a while loop, but the for loop is easier to read and more natural for counting loops. Note

28 Computer Science: A Structured Programming Approach Using C28 FIGURE 6-14 Comparing for and while Loops

29 Computer Science: A Structured Programming Approach Using C29 PROGRAM 6-4Example of a for Loop

30 Computer Science: A Structured Programming Approach Using C30 PROGRAM 6-4Example of a for Loop

31 Computer Science: A Structured Programming Approach Using C31 PROGRAM 6-5A Simple Nested for Loop

32 Computer Science: A Structured Programming Approach Using C32 PROGRAM 6-5A Simple Nested for Loop

33 Computer Science: A Structured Programming Approach Using C33 FIGURE 6-15 do…while Statement

34 Computer Science: A Structured Programming Approach Using C34 PROGRAM 6-6Two Simple Loops

35 Computer Science: A Structured Programming Approach Using C35 PROGRAM 6-6Two Simple Loops

36 Computer Science: A Structured Programming Approach Using C36 FIGURE 6-16 Pre- and Post-test Loops

37 Computer Science: A Structured Programming Approach Using C37 PROGRAM 6-7Adding a List with the do…while

38 Computer Science: A Structured Programming Approach Using C38 PROGRAM 6-7Adding a List with the do…while

39 Computer Science: A Structured Programming Approach Using C39 FIGURE 6-17 Nested Comma Expression

40 Computer Science: A Structured Programming Approach Using C40 PROGRAM 6-8Comparison of while and do…while

41 Computer Science: A Structured Programming Approach Using C41 PROGRAM 6-8Comparison of while and do…while

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