1.Factorial of a number:


/* C program to display factorial of an integer if user enters 

non-negative integer. */ #include <stdio.h> main() { int n, count; float factorial=1; printf("Enter an integer: "); scanf("%d",&n); if ( n< 0) printf("Error!!! Factorial of negative number doesn't exist."); else { for(count=1;count<=n;count++) /* for loop terminates if count>n */ { factorial*=count; /* factorial=factorial*count */ } printf("Factorial = %f",factorial); } }

Output 1

Enter an integer: -5
Error!!! Factorial of negative number doesn't exist.

Output 2

Enter an integer: 10
Factorial = 3628800

  

      2.Fibonacci series

/* Displaying Fibonacci sequence up to nth term where n is    entered by user. */#include <stdio.h>
int main()
{
  int count, n, t1=0, t2=1, display=0;
  printf("Enter number of terms: ");
  scanf("%d",&n);
  printf("Fibonacci Series: %d+%d+", t1, t2); /* Displaying first two terms */
  count=2;    /* count=2 because first two terms are already  displayed. */  while (count<n)  
  {
      display=t1+t2;
      t1=t2;
      t2=display;
      ++count;
      printf("%d+",display);
  }
  return 0;
}

Output

Enter number of terms: 10
Fibonacci Series: 0+1+1+2+3+5+8+13+21+34+