The factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. The function uses for loop to calculate the factorial and returns the number. Program terminates if a non integer number is entered. This C language program uses for loop in just a single statement to calculates the factorial of integer number.
5!= 5 x 4 x3 x2 x1 =120

Fibonacci series , 0 , 1 , 1 , 2 , 3 , 5 , 8 , 13 , 21 , 34 ………Fibonacci sequence are the numbers in the following integer sequence 0 , 1 , 1 , 2 , 3 , 5 , 8 , 13 , 21 , 34 ……… By definition, the first two numbers in the Fibonacci sequence are 0 and 1, and each subsequent number is the sum of the previous two.