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C Decision Control statement:
- In decision control statements (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,
- if statements
- if else statements
- 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 | Syntax: if (condition) { Statements; }Description: In these type of statements, if condition is true, then respective block of code is executed. | 
| if…else | Syntax: if (condition) { Statement1; Statement2; } else { Statement3; Statement4; }Description: 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 | Syntax: if (condition1){ Statement1; } else_if(condition2) { Statement2; } else Statement 3;Description: 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.
| 1 2 3 4 5 6 7 8 | 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.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | #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.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | #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 | 
