Problem Solving and Structured Programming, Slides of Advanced Computer Programming

Download Problem Solving and Structured Programming and more Slides Advanced Computer Programming in PDF only on Docsity! Chapter 9 Additional Control Structures 1 Docsity.com Chapter 9 Topics • Switch Statement for Multi-Way Branching • Do-While Statement for Looping • For Statement for Looping • Using break and continue Statements 2 Docsity.com Switch Statement • The value of IntegralExpression (of char, short, int, long or enum type) determines which branch is executed • Case labels are constant (possibly named) integral expressions • Several case labels can precede a statement 5 Docsity.com Control in Switch Statement • Control branches to the statement following the case label that matches the value of IntegralExpression • Control proceeds through all remaining statements, including the default, unless redirected with break • If no case label matches the value of IntegralExpression, control branches to the default label, if present--otherwise control passes to the statement following the entire switch statement • Forgetting to use break can cause logical errors because after a branch is taken, control proceeds sequentially until either break or the end of the switch statement occurs 6 Docsity.com Do-While Statement Do-While is a looping control structure in which the loop condition is tested after each iteration of the loop SYNTAX do { Statement } while (Expression); Loop body statement can be a single statement or a block 7 Docsity.com Do-While Loop When the expression is tested and found to be false, the loop is exited and control passes to the statement that follows the Do-while statement 10 Statement Expression DO WHILE FALSE TRUE Docsity.com For Loop SYNTAX for (initialization; test expression; update) { Zero or more statements to repeat } 11 Docsity.com For loop contains • An initialization • An expression to test for continuing • An update to execute after each iteration of the body 12 Docsity.com Example of Repetition int num; for (num = 1; num <= 3; num++) cout << num << “Potato” << endl; 15 num OUTPUT 1 Docsity.com Example of Repetition int num; for(num = 1; num <= 3; num++) cout << num << “Potato” << endl; 16 num OUTPUT 1 true Docsity.com Example of Repetition int num; for (num = 1; num <= 3; num++) cout << num << “Potato” << endl; 17 num OUTPUT 1 1Potato Docsity.com Example of Repetition int num; for (num = 1; num <= 3; num++) cout << num << “Potato” << endl; 20 num OUTPUT 2 1Potato 2Potato Docsity.com Example of Repetition int num; for (num = 1; num <= 3; num++) cout << num << “Potato” << endl; 21 num OUTPUT 3 1Potato 2Potato Docsity.com Example of Repetition int num; for(num = 1; num <= 3; num++) cout << num << “Potato” << endl; 22 num OUTPUT 3 true 1Potato 2Potato Docsity.com Example of Repetition int num; for(num = 1; num <= 3; num++) cout << num << “Potato” << endl; 25 num OUTPUT 4 false 1Potato 2Potato 3Potato Docsity.com Example of Repetition int num; for(num = 1; num <= 3; num++) cout << num << “Potato” << endl; 26 num When the loop control condition is evaluated and has value false, the loop is said to be “satisfied” and control passes to the statement following the For statement 4 false Docsity.com Output 27 The output was 1Potato 2Potato 3Potato Docsity.com Answer 30 ********** The 10 asterisks are all on one line. Why? Docsity.com What output from this loop? int count; for (count = 0; count < 10; count++); { cout << “*”; } 31 Docsity.com Answer • No output from the for loop! Why? • The semicolon after the () means that the body statement is a null statement • In general, the body of the For loop is whatever statement immediately follows the () • That statement can be a single statement, a block, or a null statement • Actually, the code outputs one * after the loop completes counting to 10 32 Docsity.com Guidelines for Choosing Looping Statement • For a simple count-controlled loop, use the For statement • For an event-controlled loop whose body always executes once, use of Do-While statement • For an event-controlled loop about which nothing is known, use a While statement • When in doubt, use a While statement 35 Docsity.com Continue Statement • The Continue statement is valid only within loops • It terminates the current loop iteration, but not the entire loop • In a For or While, Continue causes the rest of the body of the statement to be skipped; in a For statement, the update is done • In a Do-While, the exit condition is tested, and if true, the next loop iteration is begun 36 Docsity.com Problem Given a character, a length, and a width, draw a box For example, given the values ‘&’, 4, and 6, you would display &&&&&& &&&&&& &&&&&& &&&&&& 37 Docsity.com