Hey everyone.
I'm trying to create & use a static library but kind of stuck at something I can't quite grasp...

I have created library file containing just 2 functions dealing with temperature conversion. I typed the source(.c) file and the headre(.h) file & compiled them to get the library(.a) file.

Now when i use it in a new program I get a LINKER ERROR at the call to the function defined in the library.
[Linker error] undefined reference to `toFahrenheit'
ld returned 1 exit status

I'm not sure where I made the mistake... while writing the source or I'm missing something about linking?

I'm posting my codes.

Source File fore creating the library "temperature.c"
Code:
/*
temperature library file
*/

double c,f,k;

double toCelsius(double x)
{
       c = (x-32)*5/9;
       return c;
}

double toFahrenheit(double x)
{
       f = x*5/9+32;
       return f;
}
Header file "temperature.h"
Code:
/*
header file : temperature
*/
extern double toCelsius(double);
extern double toFahrenheit(double);
New Program "Test.c"
Code:
//testing temperature library
#include<stdio.h>
#include "temperature.h"

int main()
{
    double c,f;
    printf("enter Celsius\t");
    scanf("%f",&c);
    f = toFahrenheit(c);
    printf("Fahrenheit = %d",f);
    
    int ch;
    while((ch = getchar()) != '\n' && ch != EOF);
    return 0;
}


P.S.
I'm using Dev C++ v4.9.9.2
with GCC v3.4.2 on Windows 7