What feature let’s us name constants or expressions?

celcius.c

#include <stdio.h>

#define FREEZING_PT 32.0f
#define SCALE_FACTOR (5.0f / 9.0f) 
/*
we use "5.0f / 9.0f" instead of "5 / 9" because
integer division result gets truncated (no decimals)
*/

int main(void)
{
    float farenheit, celcius;

    printf("Enter Farenheight temperature: ");
    scanf("%f", &farenheit);

    celcius = (farenheit - FREEZING_PT) * SCALE_FACTOR;

    printf("Celcius equivalent: %.1f\\n", celcius);

    return 0;
}