Cannot figure out this bug "error: conflicting types"

[alter.ego]

Hi,

I am trying to work on a "simple" problem from K&R book. The excercise is as under:

Rewrite the temperature conversion program of Section 1.2 to use a function for conversion.

My attempt:

#include <stdio.h>
#include <stdlib.h>

 int main(void) {
	float fahr;
	float collector;
	int lower = 0;
	int upper = 300;
	int step = 20;
	fahr = lower;
	while (fahr <= upper)
	{
		collector = FtoC (fahr); 
		printf ("\n F is %3.0f & C is %6.1f", fahr, collector);
		fahr = fahr + step;
	}
	return 0;
}

float FtoC (float n)
{
	float c;
	c = (5.0 / 9.0) * (n - 32.0);
	return c;

}

As far as my knowledge goes, there isn't any bug in this code but compiler is returning this error & warning. I've no idea WHY? Kindly help.

/src/celsius_converter.c: In function ‘main’:
../src/celsius_converter.c:23:3: warning: implicit declaration of function ‘FtoC’ [-Wimplicit-function-declaration]
../src/celsius_converter.c: At top level:
../src/celsius_converter.c:30:7: error: conflicting types for ‘FtoC’
../src/celsius_converter.c:23:15: note: previous implicit declaration of ‘FtoC’ was here
make: *** [src/celsius_converter.o] Error 1

[ZuK]

you have to forward declare FtoC();

put

float FtoC (float n);

before main().

otherwise the compiler thinks FtoC is a function that returns int.

Kurt

[livin]

Yes the above reply is correct. On a more general level, u need to either define the function before you use it or declare it before using it in main and define it after main.

[alter.ego]

Thanks! That helped & thanks for giving reasons behind it too.