Farenheit to Centigrade

3.1 Farenheit to Centigrade

We can convert a temperature F, expressed in degrees on the Farenheit scale, to degrees Centigrade by the formula: which renders in code as







double 
f
;

⋮







double 
c 
= 
(5.0 
/ 
9.0) 
* 
(
f 
- 
32.0);

Note, by the way, the use of the constants "5.0" and "9.0" rather than just "5" and "9". That’s actually important. 5.0/9.0 is a floating point calculation that yields a floating-point answer of approximately 0.5556. But 5/9 is an integer calculation that truncates any fractional part and actually returns an answer of 0.

So if we had written







double 
f
;

⋮







double 
c 
= 
(5 
/ 
9) 
* 
(
f 
- 
32);

then, no matter how hot it gets on the Farenheit scale, we would think it’s still freezing in Centigrade!