Control Structure in C

The decision control structure in C can be implemented using
 1. The if Statement 
 2. The if - else Statement
 3. The Nested if - else Statement

The if Statement

  The general form of it statement looks like this :
   
     if(this condition is true)
            execute this statement;

The if statement by itself will execute a single statement or a group of statement when the condition following if is true.
  
The simple example of a if statement is :
    if(varName = = 20)
      printf("Value of the variable is 20");

We can use the block to specify the statement to pre executed if the given condition is true.
 if(varName = = 20)
 {
    printf("Value of the variable is 20");
    printf("Print what ever you want !!!");
 }

The if - else Statement

  The if statement by itself will execute a single statement or a group of statements when the condition following if is true. It does nothing when the condition is false. If the condition is false then a group of statements can be executed using else statement.
The following program illustrates this
 /* Calculation of gross salary */
   main( )
   {
    float bs, gs, da, hra;
    printf("Enter basic salary");
    scanf("%f", &bs);
    if(bs<1500)
    { 
          hra = bs * 10/100;
          da = bs * 90/100;
     }
    else
     {
           hra = 500;
           da = bs * 98/100;
      }
      gs = bs+hra+da;
      printf("gross salary = Rs. /.f" , gs);
     }

The Nested if - else Statement

   It we write an entire if - else construct within the body of the if statement or the body of an else statement. This is called nesting of if . For example

    if(condition)
    {
         if(condition)
          {
             do this;
          }
          else
          {
            do this;
            and this;
          }
         else
             do this;
    }