Program:

    #include<iostream.h>
    #include<conio.h>

    void main()
    {
    int num;
    unsigned long factorial=1;
    clrscr();
    cout<<"\n Enter the number: ";
    cin>>num;
    if(num<0)
    cout<<"\n"<<num<<" Factorial not denied";
    else
    {
    for(int i=1;i<=num;i++)
    factorial*=i;
    cout<<"\n Factorial of "<<num<<" is: "<<factorial;
    }
    getch();
    }