CS149D Elements of Computer Science Ayman Abdel-Hamid Department of Computer Science Old Dominion University Lecture 19: 11/5/2002 Lecture 19: 11/5/2002 CS149D Fall 2002

Outline Selection Statements cont. Switch statement Looping While statement Lecture 19: 11/5/2002 CS149D Fall 2002

Selection Statements cont. Switch statement switch (expression) { case value1: statement(s); break; case value2: statement(s); break; case valuen: statement(s); break; default: statement(s); } if ( i == 1) x = x +1; else if (i == 2) y = y +1; else if (i == 3) z = z+1; else if (i == 4) T = T +1; Is there a better way? switch(i) { case 1: x = x+1; break; case 2: y = y+1; break; case 3: z = z+1; break; case 4: T = T+1; } Can be rewritten as Lecture 19: 11/5/2002 CS149D Fall 2002

Loops Implement Repetitive structures 3 loop structures in C++ while loop, do/while loop, for loop General functionality Execute a certain block of statements until a condition is not true. Lecture 19: 11/5/2002 CS149D Fall 2002

The while loop Condition True ? Execute while Statement(s) Continue to next statement No Yes while (condition) statement; or { statements; } Infinite loop If condition is always true Lecture 19: 11/5/2002 CS149D Fall 2002

The while loop int x = 0,z = 0, y = 5; while (x < y) { z++; cout << z; x++; } What is the program output? Example to convert degrees to radians (page 73-74) Degrees range from 0 to 360 int degrees = 0; while (degrees <= 360) { radians = degrees * PI/180; degrees += 10; } Lecture 19: 11/5/2002 CS149D Fall 2002