fatal error link 1120: 1 unresolved external

[amytannx3]

I just started taking a C++ class, and I keep getting this message when I try to run my program.

fatal error link 1120: 1 unresolved external

I cant figure out what the problem is

#include<iostream>
#include<iomanip>
#include<string>
using namespace std;
int main ()
{
double TC1,TF1,TR1;
cout<<"Enter degrees celsius.\n";
cin>>TC1;
TF1=((1.8*TC)+32);
TR1=(TF1+459.7);
cout<<TR1<<"degrees Rankin\n";
return 0;
}

[zb0S216C]

Of what type is TC?

Also, what function is the compiler pointing to? A URES error is either caused by a declared, but not defined, symbol such as a static data member or function.

_Wazzak