C++ program to find the factorial, GCD and Fibonacci using recursion

/* Program to find the factorial, GCD and Fibonacci using recursion */

#include<iostream.h>
#include<conio.h>
#include<stdlib.h>
int fact(int);
int gcd(int,int);
void fib(int,int,int,int);
void main()
{
 char ch;
 clrscr();
 while(1)
 {
  cout<<"\n\n************RECURSIVE SOLUTIONS*************\n\n";
  cout<<"1.Factorial of a number \n2.Fibonacci Series\n3.GCD of 3 numbers\n4.Exit";
  cout<<"\nEnter your choice:";
  ch=getche();
  switch(ch)
  {
   case '1': cout<<"\nEnter a number:";
   int n,f;
   cin>>n;
   f=fact(n);
   cout<<"\n"<<n<<"!="<<f;
   break;

   case '2': cout<<"\nEnter the limit:";
   cin>>n;
   cout<<"\nFibonacci Series \n";
   if(n==0)
cout<<"0";
   else if(n==1)
cout<<"0,1";
   else
 {
  cout<<"0,1,";
  fib(0,1,1,n);
 }
   break;

   case '3': cout<<"\nEnter 3 numbers\n";
   int n1,n2,n3;
   cin>>n1>>n2>>n3;
   cout<<"GCD of 3 numbers is:"<<gcd(n1,gcd(n2,n3));
   break;

   case '4': exit(0);

   default : cout<<"Invalid choice!";
  }
  }
}

int fact(int x)
{
 int f;
 if(x==0)
   return 1;
 else
   f=x*fact(x-1);
 return f;
}

void fib(int n1,int n2,int n3,int l)
{
 n3=n1+n2;
 if(n3>l)
   return;
 cout<<n3<<",";
 fib(n2,n3,n3,l);
}

int gcd(int n1,int n2)
{
  if(n2==0)
    return n1;
  else if(n2>n1)
   return gcd(n2,n1);
  else
return gcd(n2,n1%n2);
}