Chapter 5: Problem 5

What is the difference between a pretest loop and a posttest loop?

Short Answer

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Answer: The main differences between a pretest loop and a posttest loop are when the conditional statement is evaluated and how this affects the execution flow of a program. In a pretest loop, the condition is evaluated before executing the loop's statements, meaning the loop may not execute its statements at all if the condition is false initially. On the other hand, in a posttest loop, the condition is evaluated after executing the loop's statements, meaning the loop will always execute its statements at least once, regardless of the initial condition.

Step by step solution

1. Define pretest loop

A pretest loop is a type of loop in which the loop's conditional statement is evaluated before executing the loop's statements. If the condition is true, the loop will continue to execute its statements. If the condition is false, the loop will not execute any statements and will exit immediately.

2. Examples of pretest loop

In most programming languages, the "while" and "for" loops are examples of pretest loops. Here's an example in Python: ```python count = 0 while count < 5: print(count) count += 1 ``` In this example, the condition `count < 5` is checked before executing the loop's statements. If the condition is false, the loop will not execute any statements.

3. Define posttest loop

A posttest loop is a type of loop in which the loop's conditional statement is evaluated after executing the loop's statements. This means that the loop will always execute its statements at least once before checking the condition. If the condition is true after executing the statements, the loop will continue to execute the statements. If the condition is false, the loop will exit.

4. Examples of posttest loop

In some programming languages, the "do-while" loop is an example of a posttest loop. Here's an example in C++: ```cpp #include using namespace std; int main() { int count = 0; do { cout << count; count++; } while (count < 5); return 0; } ``` In this example, the condition `count < 5` is checked after executing the loop's statements. The loop will always execute its statements at least once, even if the condition is false initially.

5. Differences between pretest and posttest loops

The main difference between the two types of loops is when the conditional statement is evaluated, which can affect the execution flow of a program: 1. Pretest loops evaluate the condition before executing the loop's statements, meaning the loop may not execute its statements at all. 2. Posttest loops evaluate the condition after executing the loop's statements, meaning the loop will always execute its statements at least once, regardless of the initial condition.

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What is the difference between a pretest loop and a posttest loop?

Short Answer

Step by step solution

1. Define pretest loop

2. Examples of pretest loop

3. Define posttest loop

4. Examples of posttest loop

5. Differences between pretest and posttest loops

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