1. 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

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

3. 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

4. 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

5. 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

6. 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