There is a program to print Fahrenheit-Celsius table as below.

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#include <stdio.h>
 
/* print Fahrenheit-Celsius table 
    for fahr = 0, 20, ..., 300 */
int main()
{
    int fahr, celsius;
    int lower, upper, step;
 
    lower = 0;    /* lower limit of temperature table */
    upper = 300;  /* upper limit */
    step = 20;    /* step size */
 
    fahr = lower;
    while (fahr <= upper)  {
        celsius = 5 * (fahr - 32) / 9;
        printf("%dt%dn", fahr, celsius);
        fahr = fahr + step;
    }
}

The right part of the figure is the output of this program. The Celsius temperature is computed and assigned to the variable celsius by the statement

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celsius = 5 * (fahr - 32) / 9;

The reason for multiplying by 5 and then dividing by 9 instead of just multiplying by 5/9 is that in C, as in many other languages,integer division truncates: any fractional part is discarded. Since 5 and 9 are integers, 5/9 would be truncated to zero and so all the Celsius temperatures would be reported as zero.

Reference

The C Programming Language