computer programming tcp1224 chapter 8 more on repetition structure
TRANSCRIPT
Computer ProgrammingTCP1224
Chapter 8More On Repetition Structure
Repetitive structures
•while and for loops
•Pre-test loops
•Exercises that includes earlier lectures
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Objectives• Include the posttest repetition structure in
pseudocode
• Include the posttest repetition structure in a flowchart
• Code a posttest loop using the C++ do while statement
• Nest repetition structures
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Posttest Loops
•Loops can be pretest or posttest
•Condition in a posttest loop is evaluated with each loop iteration▫Evaluation occurs after instructions within
loop are processed Also called bottom-driven loops
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Posttest Loops (continued)
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Flowcharting a Posttest Loop
•Flowcharts illustrate why loops are referred to as pretest and posttest loops▫Repetition diamond appears at the top of a
pretest loop, but at the bottom of a posttest loop
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Flowcharting a Pre-test Loop
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Flowcharting a Posttest Loop
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Flowcharting a Posttest Loop
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Coding the Posttest Loop
•Use the while statement or the for statement to code a pretest loop in C++
•Use the do while statement to code a posttest loop in C++▫The loop condition must be a Boolean
expression Can contain variables, constants, functions,
and arithmetic/comparison/logical operators
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Coding the Posttest Loop
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Posttest Loop Example
•Problem description▫In January of each year, O’Donnell
Incorporated pays a 10% bonus to each of its salespeople
▫Bonus based on amount of sales made by salesperson during previous year
▫Payroll clerk wants a program that calculates and displays each salesperson’s bonus amount
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Posttest Loop Example
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Posttest Loop Example
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Post-test in C++
do{// statements
} while ( <conditions> );
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Nested Repetition Structures
•In a nested repetition structure, one loop (inner loop) is placed entirely within another loop (outer loop)
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Nested Repetition Structures
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Nested Loop Example• Max Beauty Supply divides its sales territory into
two regions: Region 1 and Region 2
• Sales manager wants a program to enter the sales amounts for both regions, one region at a time▫Program should calculate the total amount sold
in the current region, and display that information
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Nested Loop Example
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Nested Loop Example
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Nested Loop Example
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Nested Loop Example
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Multiple level nestingwhile ( <conditions> ){// statementsfor ( <initialize>; <condition>; <counter> ){
// statementsdo{
// statements} while ( <conditions> );
}}
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Summary• A repetition structure can be a pretest or
posttest loop▫In a pretest loop, the loop condition is
evaluated before the instructions in the loop body are processed Instructions may never be processed Use while or for statements
▫In a posttest loop, the loop condition is evaluated after the instructions in the loop body are processed Instructions are always processed at least once Use the do while statement
• You can nest repetition structures
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