Temperature Conversion

tempconvert.c

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

#define C2F(c)  c *  9  / 5 + 32
#define F2C(f) (f - 32) * 5 / 9

int
main(int argc, char **argv)
{
    int ch, c_flag = 0, f_flag = 0;
    float temp;
    while((ch = getopt(argc, argv, "fct:")) != -1) {
        switch(ch) {
        case 't':
            temp = atof(optarg);
            break;
        case 'c':
            c_flag = 1;
            break;
        case 'f':
            f_flag = 1;
            break;
        }
    }
    if(c_flag == 1) {
        printf("%.2fC = %.2fF\n", temp, C2F(temp));
    }
    if(f_flag == 1) {
        printf("%.2fF = %.2fC\n", temp, F2C(temp));
    }
    return 0;
}