[Courses] [C] Beginner's Lesson Four: K's Answers to Exercises

[Akkana]

KWMelvin writes:
> 1. /* ex4-1.c -- convert degress C to degrees F */
[ ... ]
>       degF = (9 / 5) * degC + 32;

This caught my eye: if you're wondering why the program sometimes
gives the wrong answer, it lies here.  Notice that 9 and 5 are both
integers: the compiler sees two integers, and assumes that it can
get away with doing only integer math.  So this ends up being:
       degF = 1 * degC + 32;
which of course isn't what you want.

If you change it to require floating point math:
       degF = (9. / 5.) * degC + 32;
then presto, it gets the right answer!  (Actually, adding the decimal
point to either the 9 or the 5 should do it; it shouldn't need both.)

This point applies to some of the other sample programs, too.

Minor point: you don't actually have to initialize degF to zero,
because you set it again before anyone ever checks it.  
It doesn't hurt anything, though.

	...Akkana