Functional C programming

• Write a function to calculate the factorial value of any integer entered through the keyboard.
  
  #include<stdio.h>
  #include<conio.h>
  long int factorial(int n); 
  void main()
  {       
  clrscr();
  long int n,res,x;
  scanf("%ld",&n);
  res=factorial(n);
  printf("%ld",res);
  getch();
  }
  long int factorial(int n)
  {
  int rem=1,i;
    for(i=n;i>=1;i--)
    rem=rem*i;
    return rem;
    }
• Write a  function power(a,b)  to  calculate the value  of  a raised to b .
  
  #include<stdio.h>
  #include<conio.h>
  int power(int a,int b);
  void main()
  {
  clrscr();
  int i,x,sum,r,n;
  
  scanf("%d%d",&x,&n);
  r=power(x,n);
  printf("%d",r);
  getch();
  }
  int power(int a,int b)
  {
  int i,res=1;
  for(i=b;i>=1;i--)
  res=a*res;
  return res;
  }
• Write a function to calculate LCM of two numbers.
  
  #include<stdio.h>
  #include<conio.h>
  int lcm(int a,int b);
  void main()
  {
  clrscr();
  int a,b,i,x,y,res;
  scanf("%d%d",&x,&y);
  res=lcm(x,y);
  printf("LCM is:\n%d",res);
  getch();
  }
  
  int lcm(int a,int b)
  {
  int i;
  for(i=1; ;i++)
  {
  if(i%a==0&&i%b==0)
  break;
  }
  return i;
  }
• Write a function to calculate GCD of two numbers.
  #include<stdio.h>
  #include<conio.h>
  int gcd(int a,int b);
  void main()
  {
  clrscr();
  int x,y,res;
  scanf("%d%d",&x,&y);
  
  res=gcd(x,y);
  printf("%d",res);
  
  getch();
  }
  int gcd(int a,int b)
  {
  int rem;
      while(b>0)
      {
      rem=a%b;
      a=b;
      b=rem;
        }
  return a;
  }
• Any year is entered through the keyboard.Write a function to determine whether the year is a leap year or not.
  #include<stdio.h>
  #include<conio.h>
  int year(int y);
  void main()
  {
  clrscr();
  int y,res;
  printf("Enter the value of year?\n");
  scanf("%d",&y);
  res=year(y) ;
  
  
  getch();
  }
  int year(int y)
  {
  
  if(y%400==0)
  return    printf("It is leap year");
  else if(y%100==0)
  return    printf("It is not leap year");
  else if(y%4==0)
  return    printf("It is leap year");
  
  else
  return    printf("It is not leap year");
  }
• A prime integer is entered through the keyboard.Write a function  to obtain the prime factors  of this number.
  
  #include<stdio.h>
  #include<conio.h>
  
  int prime (int x);
  void main()
  {
  clrscr();
  int num;
  printf("Enter The Number:");
  scanf("%d",&num);
  int p,i;
  p=num;
  for(i=2;i<=(num/2);i++)
  {  if(prime(i))
     while(p%i==0)
       { printf("%d ",i);
         p=p/i;
       }
  
  }
  getch();
  }
  
  int prime (int x)
  {  int i=2;
     while(i<=(x/2))
       { if(x%i==0)
         break;
         ++i;
       }
     if (i>(x/2))
     return 1;
     else
     return 0;
  }
• Write a function which receives 5 integers and returns the sum, average and standard deviation of these numbers. Call this function from main() and print the results in main().
  #include<stdio.h>
  #include<conio.h>
  #include<math.h>
  int sum(int p,int q,int r,int s,int t);
  float average(float o);
  float sd(float m,float n);
  
  void main()
  {
  clrscr();
  int a,b,c,d,e,x;
  float y,z;
  printf("Enter the value of a:");
  scanf("%d",&a);
  printf("Enter the value of b:");
  scanf("%d",&b);
  printf("Enter the value of c:");
  scanf("%d",&c);
  printf("Enter the value of d:");
  scanf("%d",&d);
  printf("Enter the value of e:");
  scanf("%d",&e);
  x=sum(a,b,c,d,e);
  printf("\nSUM=%d",x);
  y=average(x);
  printf("\nAVERAGE=%f",y);
  z=sd(x,y);
  printf("\nSTANDARD DEVIATION=%f",z);
  
  getch();
  }
  int sum(int p,int q,int r,int s,int t)
  {
      return p+q+r+s+t;
  }
  float average(float o)
  {
      return o/5;
  }
  float sd(float m,float n)
  {
      return (sqrt(m-n));
  }
• A 5 digit positive integer is entered through the keyboard write a function to calculate sum of digits of the digit number.
  Using recursion:
  #include<stdio.h>
  #include<conio.h>
  int digitsum(int n);
  
  void main()
  {
    clrscr();
    int x;
    printf("Enter The Number:");
    scanf("%d",&x);
    printf("The Sum Is:%d",digitsum(x));
    getch();
  }
  
  int digitsum(int n)
  
  {
    int rem,sum;
    if(n==0)
       return 0;
    rem=n%10;
    n=n/10;
    sum=rem+digitsum(n);
    return sum;
  }
  
  Without using recursion:
  #include<stdio.h>
  #include<conio.h>
  int digitsum(int n);
  
  void main()
  {
    clrscr();
    int x;
    printf("Enter The Number:");
    scanf("%d",&x);
    printf("The Sum Is:%d",digitsum(x));
    getch();
  }
  
  int digitsum(int n)
  
  {
    int rem,sum=0,i;
    for (i=1;i<=5;i++)
    { rem=n%10;
      n=n/10;
      sum=sum+rem; }
    return sum;
  }
• A positive integer is entered through the keyboard, write a program  to obtain the prime factors recursively.
  #include<stdio.h>
  #include<conio.h>
  primefct(int x);
  void main()
  {
  clrscr();
  int x;
  printf("Enter an integer:");
  scanf("%d",&x);
  printf("the prime factors are:");
  primefct(x);
  getch();
  }
  
  primefct(int n)
  {
  int i;
  for(i=2;i<=n;i++)
  {
   if(n%i==0)
      {
      printf("%d ",i);
      primefct(n/i);
      break;
      }
  }
  }
• Write a recursive function to obtain the first 25 numbers of a Fibonacci  sequence.In a Fibonacci sequences the sum of two successive terms given the third term. Following are the first few term of the Fibonacci sequence:
  1         1          2           3           5           8          13           21           34          55.........
  
  #include<stdio.h>
  #include<conio.h>
  
  long int fib(long int m);
  void main()
  {
  clrscr();
  long int i;
  for(i=1;i<=25;i++)
     printf("\n%ld\n",fib(i));
  getch();
  
  }
  long int fib(long int m)
  {
  if(m<=2)
     return 1;
  else
     return fib(m-1)+fib(m-2);
  
  }