Recursive Function

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Definition

A function which calls itself is called as recursive function.

Description

• Are slower in speed becuase of stack overhead.
• Should have recursive expression with terminating statement.

Source code

Program working steps

• First line is the comment, 2nd and 3rd line are preprocessor directives which holds definition of functions like clrscr(), printf(), scanf() etc.
• void main() is the funtion, where program execution starts.
• Declaration of variable number to store input number and fact to display the required result.
• clrscr() function to clear the screen like cls in windows and clear in linux.
• Next two statements takes the input from the user and stores the value into variable number.
• Line no.11 calls the factorial function by passing number variable to it. So the program control transfers to line no.15, where a block of code for calculating the factorial of a number is written.
• factorial function takes one argument from the caller function and stores the value into the variable n of integer data-type.
• First is the terminating condition if(n<2) then break recursive loop, else part contains recursive expression return n*factorial(n-1) which calls itself.
• Suppose the user enters 4 as a value then the factorial function will work like,
  Fist the terminating condition
  if(4<2) is false so it will execute else part
  4*factorial(4-1)
  this statement calls the factorial function with(4-1)as a argument, so it will again start from first statement.
  if(3<2) now the value of n is decrease by one, but still condition is false so it will execute else part.
  3*factorial(3-1) This statement again calls itself.
  This will keep repeating till terminating condition becomes true i.e. when n = 1. Then the function will return the calculated value using return f; statement.
  A closer lookup of the recursive calls
  f=4*factorial(4-1);
  f=4*3*factorial(3-1);
  f=4*3*2*factorial(2-1);
  f=4*3*2*1;
  f=16;
• This calculated f value will be return back to calling functoin to line no.11, where value of fact will be 16.
• Next printf statement prints the quoted text, 'Factorial of given number is 16.'.
• getch() to wait input character to exit the program.

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