1. If statement

2. Conditional Expressions
If statement uses conditions
A condition is an expression that can be evaluated to be
TRUE (any value > 0) or
FALSE (value of 0)
Conditional Expression is composed of expressions combined with relational and/or logical operators

3. Relational Operators == equality (x == 3) != non equality (y != 0)
< less than (x<y)
> greater than (y>10)
<= less than equal to (x<=0)
>= greater than equal to (x>=y)
!!! a==b vs. a=b !!!

4. Examples
a < b
x+y >= k/m
fabs(denum) <

5. Logical Operators ! not !(x==0) && and (x>=0) && (x<=10)
|| or (x>0) || (x<0) A B
A && B
A || B !A !B
False
True

6. Examples a<b<c is not the same as (a<b) && (b<c)
a+b * 2 < 5 && 4>=a/2 || t-2 < 10
a=3, b=5, t=4

7. Precedence for Arithmetic, Relational, and Logical Operators

8. Exercise Assume that following variables are declared
a = 5.5 b = k = -3
Are the following true or false
a < k
a + b >= 6.5
k != a-b
!(a == 3*b)
a<10 && a>5
fabs(k)>3 || k<b-a

9. If statement if(Boolean expression) statement; //single statement
{ //more than one statement
statement1; .
statement n; }

10. Examples if (x>0) { x=sqrt(x); } k++; 4 2 x k -2 2 x k 4 2 x k -2 2

11. if - else statement if (boolean expression) statement1; else{
statement block1 }
statement block2
x=y;
x=y;
k=3;

12. If-else statement
What does the following program do? Assume that x, y, temp are declared.
if (x>y)
temp = x;
else
temp = y; 1 3 ? x y
temp 3 1 ? x y
temp

13. If-else statement Split the following statement into two separate if
if (x>y)
temp = x;
else
temp = y;
if (x>y)
temp = x;
if (x<=y)
temp = y;

14. Exercise
Write an if-else statement to find both the maximum and minimum of two numbers. Assume that x,y, min, max are declared.
if (x>y) Ex: x = 10, y = 5
{ y = 3, y = 4
max = x; x = 6, y = 6
min = y; }
else {
max = y;
min = x;

15. nested if-else if(x > y) if(y < z) k++; if (y<z) k++; else
m++;
j++;
if (y<z)
k++;
else
m++;

16. Exercise int x=9, y=7, z=2, k=0, m=0, j=0; if (x > y) if(y < z)
else
m++;
j++;
What are the values of j, k and m after execution of if statement? 9 7 x y 2 z k m j

17. Exercise int x=3, y=7, z=2, k=0, m=0, j=0; if (x > y) if(y < z)
else
m++;
j++;
What are the values of j, k and m after execution of if statement? 3 7 x y 2 z k m j

18. Exercise
Given a score and the following grading scale write a program to find the corresponding grade. A B C
0-39 D

19. Solution if ((score >= 80) && (score <=100)) grade = 'A';
grade = 'B';
if ((score >= 40) && (score <= 59))
grade = 'C';
if ((score >= 0) && (score <= 39))
grade = 'D';

20. Nested if - else statement
if (boolean expression) {
statement block1 }
else if (boolean expression2 {
statement block2
else if (Boolean expression3) {
statement block3
else {
statement block4

21. Solution if ((score >= 80) && (score <=100)) grade = 'A';
else if ((score >= 60) && (score <= 79))
grade = 'B';
else if ((score >= 40) && (score <= 59))
grade = 'C';
else if ((score >= 0) && (score <= 39))
grade = 'D';
else
grade = ‘I’;

22. Alternate Solution grade = ‘I’; else if (score >= 80) grade = 'A';
grade = 'B';
else if (score >= 40)
grade = 'C';
else if (score >= 0)
grade = 'D';
else

23. Exercise
Write a program that reads 3 numbers a, b and c from user and computes minimum, maximum and median of the numbers.
Example:
a = 2, b = 5, c = 3
minimum = 2, maximum = 5, median = 3
a = 2, b = 2, c = 3
minimum = 2, maximum = 3, median = 2

24. Exercise continued Find minimum of 3 numbers
Write an if statement to check if minimum is a
if (condition) what should
min = a; be condition?
Write an if statement to check if minimum is b
Write an if statement to check if minimum is c
Combine 1-3 into a single nested if-else statement
Similarly find maximum of 3 numbers
Find median of 3 numbers

25. Minimum if ((a<b) && (a<c)) min = a;
else if ((b<a) && (b<c))
min = b;
else if ((c<a) && (c<b))
min = c;

26. Maximum if ((a>b) && (a>c)) max = a;
else if ((b>a) && (b>c))
max = b;
else if ((c>a) && (c>b))
max = c;

27. Median median = b; else if ((c<b) && (b<a))
if ((a<b) && (b<c))
median = b;
else if ((c<b) && (b<a))
else if ((b<a) && (a<c))
median = a;
else if ((c<a) && (a<b))
else if ((b<c) && (c<a))
median = c;
else if ((a<c) && (c<b))

28. Alternate Solution for Median
if (((a<b) && (b<c)) || ((c<b) && (b<a)))
median = b;
else if (((b<a) && (a<c)) || ((c<a) && (a<b)))
median = a;
else if (((b<c) && (c<a)) || ((a<c) && (c<b)))
median = c;

29. Exercise
Write a program that reads a point (x, y) from user and prints the region it resides in.
For example
Enter x, y: 3 -1
Point in Region 4
Enter x, y: -1 -5
Point in Region 3
Region 2
Region 1
Region 3
Region 4

30. Solution if ((x>0) && (y>0)) printf("Region 1\n");
else if ((x<0) && (y>0))
printf("Region 2\n");
else if ((x<0) && (y<0))
printf("Region 3\n");
else if ((x>0) && (y<0))
printf("Region 4\n");

31. Alternate Solution if (x>0) if (y>0) printf("Region1\n"); else