111/18/2015CS150 Introduction to Computer Science 1 Announcements  I have not graded your exam yet

211/18/2015CS150 Introduction to Computer Science 1 Multiple Alternative Ifs if (condition1) statement1; else if (condition2) statement2; … else defaultstatement;

311/18/2015CS150 Introduction to Computer Science 1 Program  Write a program that displays a letter grade corresponding to an exam score A B C D 0-59 F

411/18/2015CS150 Introduction to Computer Science 1 Example if (salary < 0.00) tax = -1; else if (salary < ) tax = 0.15 * salary; else if (salary < ) tax = (salary )* ; else tax = salary * 0.26;

511/18/2015CS150 Introduction to Computer Science 1 What’s the difference? if (x >= 0) x = x + 1; else if (x >= 1) x = x + 2; if (x >= 0) x = x + 1; if (x >= 1) x = x + 2;

611/18/2015CS150 Introduction to Computer Science 1 Selection Structure Review  Write a program to solve the following problem: A police department needs to calculate fees for speeding tickets. The fees are as follows: SpeedFee 75 or greater$ $ $20.00

711/18/2015CS150 Introduction to Computer Science 1 Switch Statements  Another form of selection statement  Similar to if’s  Useful for lots of alternatives

811/18/2015CS150 Introduction to Computer Science 1 Example switch (watts) { case 25: life = 2500; break; case 40: case 60: life = 1000; break; case 75: case 100: life = 750; break; default: life = 0; }

911/18/2015CS150 Introduction to Computer Science 1 Form switch (selector) { case label1: statements1; break; case label2: statements2; break; … case labeln: statementsn; break; default: statements; }

1011/18/2015CS150 Introduction to Computer Science 1 Example switch (musical_note) { case ‘c’: cout << “do” << endl; break; case ‘d’: cout << “re” << endl; break; case ‘e’: cout << “mi” << endl; break; case ‘f’: cout << “fa” << endl; break; case ‘g’: cout << “sol” << endl; break; case ‘a’: cout << “la” << endl; break; case ‘b’: cout << “ti” << endl; break; default: cout << “An invalid note was read.”; }

1111/18/2015CS150 Introduction to Computer Science 1 Important!  Selector must be ordinal type  Each possible value is a separate case  break stops statements for case, otherwise continue with statements for next case

1211/18/2015CS150 Introduction to Computer Science 1 Example switch (color) { case ‘R’: case ‘r’: cout << “red” << endl; case ‘B’: case ‘b’: cout << “blue” << endl; case ‘Y’: case ‘y’: cout << “yellow” << endl; } What happens when color is ‘r’? ‘B’? ‘Y’?

1311/18/2015CS150 Introduction to Computer Science 1 Example switch (x > y) { case 1: cout << “x greater” << endl; break; case 0: cout << “y greater or equal” << endl; break; } Write as if statement

1411/18/2015CS150 Introduction to Computer Science 1 Questions  Can you write any switch statement as an if?  Can you write any if statement as a switch?

1511/18/2015CS150 Introduction to Computer Science 1 Problem  Write a switch statement to convert a character digit to an integer

1611/18/2015CS150 Introduction to Computer Science 1 Change to switch if (speed > 35) fee = 20.00; else if (speed > 50) fee = 40.00; else if (speed > 75) fee = 60.00;

1711/18/2015CS150 Introduction to Computer Science 1 Examples  Write an if statement that prints out the level of schooling. (0, none; 1 through 6, elementary; 7 through 8, middle school; 9 through 12, high school; > 12, college)  Write a switch statement to do the same

1811/18/2015CS150 Introduction to Computer Science 1 Write a Program Input an integer If the integer is positive, increment a variable poscount by 1. If the integer is negative, increment a variable negcount by 1. If neither, increment zerocount by 1.

1911/18/2015CS150 Introduction to Computer Science 1 Unary Operators ++ and --  ++ is increment operator x++; is the same as x = x + 1;  -- is decrement operator x--; is the same as x = x - 1;

2011/18/2015CS150 Introduction to Computer Science 1 Prefix and Postfix Unary ++ and -- PrefixPostfix k = --x;k =x--; k = ++x;k = x++; Increment/Assign value of x to decrement xk, then increment then assignor decrement x value of x to k

2111/18/2015CS150 Introduction to Computer Science 1 Example cout << “Value of i is” << i; cout << “Value of i++ is” << i++; cout << “Value of ++i is” << ++i; cout << “Value of --i is” << --i; cout << “Value of i-- is” << i--;

2211/18/2015CS150 Introduction to Computer Science 1 Program  Write a program that outputs the following: *****

2311/18/2015CS150 Introduction to Computer Science 1 count = 0; while (count < 5) { cout << “ ***** ” << endl; count++; } How many times (iterations) does loop run? Loops Loop Control Variable Initialize LCV Change the value of count

2411/18/2015CS150 Introduction to Computer Science 1 While loops while (logical expression is true) statement; while (logical expression is true) { statement1; statement2; … }

2511/18/2015CS150 Introduction to Computer Science 1 Key ingredients  Initialize MUST initialize loop control variable  Test The value of loop control variable is tested during each iteration of loop  Update Loop control variable is changed during each loop iteration If any one of these is missing or incorrect, your loop won’t run properly--not at all, too many/few times or infinitely.

2611/18/2015CS150 Introduction to Computer Science 1 Examples  Write a while loop that outputs each integer from 1 to 5  Write a program that inputs the following data for 5 students: name, id# and grade  Write a program that inputs the following data for a user specified number of students: name, id# and grade