if statement :

The if statement controls conditional branching. The body of an if statement is executed if the value of the expression is nonzero. Or if statement is used to execute the code if condition is true. If the expression/condition is evaluated to false (0), statements inside the body of if is skipped from execution. 

Syntax : 

if(condition/expression) 

{ 

true statement; 

}

 statement-x; 

If the condition/expression is true, then the true statement will be executed otherwise the true statement block will be skipped and the execution will jump to the statement-x. The „true statement‟ may be a single statement or group of statement. 

If-else statement :

The if-else statement is an extension of the simple if statement. The general form is. The if...else statement executes some code if the test expression is true (nonzero) and some other code if the test expression is false (0) .

Syntax : 

if (condition) 

{ 

true statement;

 } 

else 

{ 

false statement; 

} 

statement-x ;

If the condition is true , then the true statement and statement-x will be executed and if the condition is false, then the false statement and statement-x is executed. 

Nested if-else statement :

When a series of decisions are involved, we may have to use more than on if-else statement in nested form. If –else statements can also be nested inside another if block or else block or both .