C++ ta hesap makinesi

#include <iostream.h>
#include <stdlib.h>
int main() //hesap makinesi
{ //
int n;
long int a,b;
cout<<"Bu hesap makinesi dir!! >>>adasd<<<"<<endl;
cout<<"Asagidaki islemilerden birini seciniz:"<<endl<<endl;
cout<<"Toplama islemi icin=1"<<endl;
cout<<"Cikarma islemi icin=2"<<endl;
cout<<"Carpma islemi icin=3"<<endl;
cout<<"Bolme islemi icin=4"<<endl<<endl;
cout<<"Kare koku icin=5"<<endl;
cout<<"Kare alma islemi icin=6"<<endl;
cin>>n;
if(n>=5)
{
cout<<"Sadece tek sayi giriniz"<<endl;
cin>>a;
}
else
{
cout<<"Ilk sayi'yi giriniz"<<endl;
cin>>a;
cout<<"Ikinci sayi'yi giriniz"<<endl;
cin>>b;
}

switch(n){
case 1:{cout<<"Sonuc="<<a+b<<endl;break;}
case 2:{cout<<"Sonuc="<<a-b<<endl;break;}
case 3:{cout<<"Sonuc="<<a*b<<endl;break;}
case 4:{cout<<"Sonuc="<<a/b<<endl;break;}
case 5:{cout<<"Sonuc="<<sqrt(a)<<endl;break;}
case 6:{cout<<"Sonuc="<<a*a<<endl;break;}

defult:cout<<"yanlis tusa bastin heralde"<<endl;break;}
cout<<"bu programi >>>PROGRAMCI <<< yapmistir..."<<endl<<endl;
system("PAUSE");
return 99;
}