Thread: Critique my program

I'm trying to learn C on my own, at my own pace (as I never really grasped it while at college). I've been reading Ritchie & Kernighan's "The C Programming Language".

I made a short program to convert a range of Fahrenheit temperatures to Celsius. It seems to compile and run OK using gcc in Linux. I'm wondering if someone could 'critique' my code, let me know if I am doing anything wrong. In particular, is it safe to convert an int to a float, like I did below, where function 'celsius' takes an int and returns a float to main?

Code:

/*a wee program to convert a range of Fahrenheit temperatures
(-100 to 300 to be exact, in 20 degree increments) to Celsius*/

#include <stdio.h>

float celsius(int); /*function prototype*/

main()
{
    int f;

    for (f = -100; f <= 300; f = f + 20)
        printf("%d\t%.2f\n", f, celsius(f));
    return 0;
}

/*function celsius definition*/
float celsius(int f)
{
    float c;

    c = (5.0/9.0) * (f - 32.0);
    return c;
}