So I just downloaded DEVc++, just using an example my teacher has given during class to check if it works. Now that it didn't work and I don't know why. I tried to looking for answers about linking error online, but I can't understand the answers.

So here is the program:

//Program to convert from Fahrenheit to Celcius
#include <iostream>

double fahrenToCelsius (double t);
//t is a valid tempreture in Fahrenheit
//returns equivalent temp. in Celcius

int main ()
using namespace std;
double f;

cout<< "Enter temp. in degrees Fahrenheit. ";
cin >> f;
cout<< f << "in degs. Fahrenheit = "
<< fahrenToCelsius (f) << "in degs. Celcius" ;

return 0;

double fahrenToCelcius (double t)
double c;
c= (t-32.0)*(5.0/9.0);
return c;

And here is the problem:
[Linker error] C:\Users\Owner\AppData\Local\Temp\cckex8SZ.o:fahrenToCelsius.cpp: (.text+0x3d): undefined reference to `fahrenToCelsius(double)'
collect2: ld returned 1 exit status

I'm suspecting the program maybe that I saved it wrong? I saved it as fahrentoCelsius.cpp inside the folder "Work" ( I created this folder) which is inside the folder "Dev-cpp".