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;
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CS150 Introduction to Computer Science 1

2. Prefix and Postfix Unary ++ and --
Prefix Postfix
k = --x; k =x--;
k = ++x; k = x++;
Increment/ Assign value of x to
decrement x k, then increment
then assign or decrement x
value of x to k
11/27/2018
CS150 Introduction to Computer Science 1

3. CS150 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--;
11/27/2018
CS150 Introduction to Computer Science 1

4. CS150 Introduction to Computer Science 1
Program
Write a program that outputs the following:
*****
11/27/2018
CS150 Introduction to Computer Science 1

5. CS150 Introduction to Computer Science 1
Loops
Initialize LCV
Loop Control Variable
count = 0;
while (count < 5) {
cout << “*****” << endl;
count++; }
How many times (iterations) does loop run?
Change the value of count
11/27/2018
CS150 Introduction to Computer Science 1

6. CS150 Introduction to Computer Science 1
While loops
while (logical expression is true)
statement; {
statement1;
statement2; … }
11/27/2018
CS150 Introduction to Computer Science 1

7. CS150 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.
11/27/2018
CS150 Introduction to Computer Science 1

8. CS150 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
11/27/2018
CS150 Introduction to Computer Science 1