Chapter 7: The Repetition Structure Introduction to Programming with C++ Fourth Edition

Introduction to Programming with C++, Fourth Edition 2 Objectives Include a repetition structure in pseudocode and in a flowchart Code a pretest loop using the C++ while statement Initialize and update counters and accumulators Code a pretest loop using the C++ for statement

Introduction to Programming with C++, Fourth Edition 3 Using the Repetition Structure Repetition structure or loop - allows repeated processing of one or more program instructions until some condition is met Repetition structure can be either a pretest loop or a posttest loop –Pretest loop: evaluation occurs before loop instructions are processed –Posttest loop: evaluation occurs after loop instructions are processed

Introduction to Programming with C++, Fourth Edition 4 Pretest Loops

Introduction to Programming with C++, Fourth Edition 5 Pretest Loops (continued)

Introduction to Programming with C++, Fourth Edition 6 Pretest Loops (continued) Every loop has: –a loop condition –a loop body Loop body: –instructions within a loop Loop condition: –appears at the beginning of a pretest loop –determines the number of times instructions within the loop are processed

Introduction to Programming with C++, Fourth Edition 7 Sentinel value – special value to end the loop Priming read: –Appears above the loop –Used to prepare or set up the loop Pretest Loops (continued)

Introduction to Programming with C++, Fourth Edition 8 Components of a Loop

Introduction to Programming with C++, Fourth Edition 9 O’Donnell Incorporated Algorithm Shown in Flowchart Form

Introduction to Programming with C++, Fourth Edition 10 Using the while Statement to Code the Pretest Loop While statement: programmer must supply the loop condition to be evaluated Loop condition: –must be a Boolean expression (true or false) –can contain variables, constants, functions, methods, arithmetic operators, comparison operators, and logical operators Endless or infinite loop – one that processes its instructions indefinitely

Introduction to Programming with C++, Fourth Edition 11 Syntax of the C++ while Statement

Introduction to Programming with C++, Fourth Edition 12 Using Counters and Accumulators Counter - a numeric variable used for counting Accumulator - a numeric variable used for accumulating a value Initializing - assigning a beginning value to the counter or accumulator Updating or incrementing - adding a number to the value stored in the counter or the accumulator

Introduction to Programming with C++, Fourth Edition 13 Counter-Controlled Pretest Loops

Introduction to Programming with C++, Fourth Edition 14 Using the for Statement to Code a Pretest Loop Most common use for the for statement: –Code pretest loops whose processing is controlled by a counter For statement: –Begins with the for clause –Followed by the body of the loop If the loop body contains more than one statement: –Statements must be entered as a statement block i.e., enclosed in braces ({})

Introduction to Programming with C++, Fourth Edition 15 Syntax of the C++ for statement

Introduction to Programming with C++, Fourth Edition 16 for Statement Displays the Numbers 1 Through 3

Introduction to Programming with C++, Fourth Edition 17 for Statement Calculates and Displays a Commission

Introduction to Programming with C++, Fourth Edition 18 for Statement Calculates and Displays a Bonus

Introduction to Programming with C++, Fourth Edition 19 Summary Repetition structure or loop - allows repeated processing of one or more program instructions until some condition is met –Repetition structures contain a condition and a loop body