If-else Statement

What is  if-else statement 

• The if-else statement is used to carry out a logical test and then take one of two possible actions depending on the outcome of the test (ie, whether the outcome is true or false).
• In C if else control statement, group of statements are executed when condition is true.  If condition is false, then else part statements are executed.
• If the condition specified in the if statement evaluates to true, the statements inside the if-block are executed and then the control gets transferred to the statement immediately after the if-block. 
• Even if the condition is false and no else-block is present, control gets transferred to the statement immediately after the if-block.
• The else part is required only if a certain sequence of instructions needs to be executed if the condition evaluates to false.

Syntax:

Flowchart of if-else statement in C

Example program for if else statement in C:

#include<stdio.h>
#include<conio.h>
void main( )
{
int a;
printf("n Enter a number:");
scanf("%d", &a);
if(a>0)
{ printf( "n The number %d is positive.",a);
}
else
{
printf("n The number %d is negative.",a);
}getch();
}

/*The following program compares two strings to check whether they are equal or not.*/

#include <stdio.h>
#include <string.h>
#include <conio.h>
void main( )
{char a[20] ,  b[20];
printf("n Enter the first string:");
scanf("%s",a);
printf("\n Enter the second string:");
scanf("%s",b);
if((strcmp(a,b)==0))
{
printf("\nStrings are the same");
}
else
{
printf("\n Strings are different");
}
getch();
}

/*The following program checks whether the entered number is positive or negative.*/

#include <stdio.h>
int main()
{ 
 if (m == n)
 int m=40,n=20;  
{  
printf("m and n are equal");
}  
else   
{  
printf("m and n are not equal");
} 
 }

Output:

m and n are not equal

Let's see the simple example of even and odd number using if-else statement in C language.

#include<stdio.h>  
#include<conio.h>  
void main()
{  
int number=0;  
clrscr();
printf("enter a number:");  
scanf("%d",&number);  
if(number%2==0)
{  
printf("%d is even number",number);  
}
else
{  
printf("%d is odd number",number);  
}getch();
}

Output

enter a number:4
4 is even number
enter a number:5
5 is odd number