“If”, “else” and “nested if” decision control statements in C

• In decision control statements (C if else and nested if), group of statements are executed when condition is true.  If condition is false, then else part statements are executed.
• There are 3 types of decision making control statements in C language. They are,

1.   if statements
2.   if else statements
3.   nested if statements

“If”, “else” and “nested if” decision control statements in C:

• Syntax for each C decision control statements are given in below table with description.

Decision control statements	Syntax	Description
if	if (condition)  { Statements; }	In these type of statements, if condition is true, then respective block of code is executed.
if…else	if (condition)  { Statement1; Statement2; }  else  { Statement3; Statement4; }	In these type of statements, group of statements are executed when condition is true.  If condition is false, then else part statements are executed.
nested if	if (condition1){ Statement1; } else_if(condition2)  { Statement2; }  else Statement 3;	If condition 1 is false, then condition 2 is checked and statements are executed if it is true. If condition 2 also gets failure, then else part is executed.

Example program for if statement in C:

      In “if” control statement, respective block of code is executed when condition is true.

int main()
{
  int m=40,n=40;
  if (m == n)
  {
  printf("m and n are equal");
  }
}

Output:

m and n are equal

Example program for if else statement in C:

      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.

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

}

Output:

m and n are not equal

Example program for nested if statement in C: 

• In “nested if” control statement, if condition 1 is false, then condition 2 is checked and statements are executed if it is true. 
• If condition 2 also gets failure, then else part is executed.

#include <stdio.h>
int main()
{
  int m=40,n=20;
  if (m>n) {
 printf("m is greater than n");
  }
  else if(m<n) {
  printf("m is less than n");
  }
  else {
  printf("m is equal to n");
  }
}

 Output:

m is greater than n