Programming C if-else statement

1. Presentation Topic: If-else

2. C if else
Introduction:-
The if statement is used to conditionally execute a statement or a
block of statements. Conditions can be true or false, execute one
thing when the condition is true, something else when the
condition is false.

3. C if else
Syntax:-
if (expression)
statement(s);
[else statement(s);]

4. C if else
Example :-
if (a == b)
printf ("%d is equal to %d", a, b);
else
printf ("%d is not equal to %d", a, b);

5. C if else
If-then statements :-
Syntax:-
if
(expression)
statement(s);

6. C if else
Note : There is no indentation rule in writing C programming, we can write the above
code in following ways :
If-then statements :-
Example:-
if (a == b)
printf ("%d is equal to %d", a, b);
else
printf ("%d is not equal to %d", a, b);

7. C if else
If-then statements :-
Example:-
if (a == b)
printf ("if a is equal to b");
printf ("%d is equal to %d", a, b);
if (a == b)
{
printf ("if a is equal to b"); printf
("%d is equal to %d", a,
b);
}
Note : The second way of writing code is a good practice.

8. C if else
#include<stdio.h>
main()
{
int num;
printf("Input a number : "); scanf("%d",&num); if(num>0)
{
printf("This is a positive integern");
}
else // else portion of if statement
{
printf(" This is not a positive integer..Try againn")
;
}
}
A complete example on conditional if-else statement:-
Example :-

9. C if else
►#include<stdio.h>
►main()
►{
►int num;
►printf("Input a number : "); scanf("%d",&num); if(num>0)
►{
►printf("This is a positive integern");
►}
►else // else portion of if statement
►{
►printf(" This is not a positive integer..Try againn")
►;
►}
►}
A complete example on conditional if-else statement:-
Example :-

10. C if else
Sequential if-then statements:-
Example :-
if (a == b)
printf ("a = b");
if (a == c)
printf ("a = c");
if (b == c)
printf ("b = c")

11. C if else
Multiway if-else-Statement :-
syntax :-
if (expression_1)
statement_1
else if (expression_2)
statement_2
.
.
.
else if (expression_n)
statement_n
else
other_statement

12. #include<stdio.h> main()
{
int num;
printf("Input score :"); scanf("%d",&num);
if (num>=90)
{
printf("Grade : Excellent");
}
else if(num>=80 && num<90)
{
printf("Grade : Very Good");
}
else if(num>=60 && num<80)
{
printf("Grade : Good");
}
else if(num>=50 && num<60)
{
printf("Grade : Average");
}
else if(num>=40 && num<50)
{
printf("Grade : Poor");
}
else
{
Multiway if-else-Statement :-
Example :-
C if else

13. C if else
Example
:-
#include<stdio.h>
main()
{
int num1=5, num2=3, num3=-12, min;
if(num1<num2)
{
if(num1<num3)
min = num1; else
min = num3;
}
else
{
if(num2<num3)
min = num2;
else
min = num3;
}
printf("Among %d, %d, %d minimum number is %d",num1
,num2,num3,min);
}
Nested if-then-else statements :-