C Code snippet to generate midi to freq, and vice versa

midi2freq.c

#include <stdio.h>
#include <math.h>

int main(){
        double semitone_ratio, c0, c5, frequency, fracmidi;
        int midinote = 73;

       semitone_ratio = pow(2, 1/12.0);
       c5 = 220.0 * pow(semitone_ratio, 3);
       c0 = c5 * pow(0.5, 5);

       frequency = c0 * pow(semitone_ratio, midinote);
       //and in reverse
       fracmidi = log(frequency / c0) / log(semitone_ratio);
       midinote = ( int)(fracmidi + 0.5);
}