Como usar Constante simbólica

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

#define LOWER 0
#define UPPER 300
#define STEP 20
int main()
{
    int fahr;
    for(fahr = LOWER; fahr <= UPPER; fahr = fahr + STEP)
        printf("%3d %6.1f\n", fahr, (5.0/9.0) * (fahr - 32));
}