Section 1.2 Variables and Arithmetic Expressions


This program uses the formula C=(5/9)(F-32) to print the Fahrenheit temperatures and their centigrade or Celsius equivalents.


/* Temperature Conversion Program, Fahrenheit to Celsius */

#include <stdio.h>

/* print Fahrenheit-Celsius table for fahr = 0,20 ... 300 */

int main() {
    int lower, upper, step;
    int celsius, fahr;

    lower = 0;
    upper = 300;
    step = 20;

    fahr = lower;

    while (fahr <= upper) {
        celsius = 5 * (fahr - 32) / 9;
        printf("%d\t%d\n", fahr, celsius);
        fahr = fahr + step;

    return 0;


In this program we are going to convert a given Fahrenheit temperature to Celsius temperature using the formula C=(5/9)(F-32) To do this we declare some variables in the beginning of the program so that they can be used in the later stages of the program. The variables in this program are: lower,upper,step, celsius,fahr.

The variable lower is assigned the value 0 similarly upper to 300, step to 20, and fahr to lower. So when the program enters the while loop it checks whether fahr <= upper is true if it is true then it assigns the variable celsius 5 * (fahr - 32) / 9 and then it prints out put.