Static, define, and const in C

Question

I\'ve read that static variables are used inside function when one doesn\'t want the variable value to change/initialize each time the function is called. But what about def

Answer 1

If the value of m has to stay the same forever, then of course you can either use

static const double m = 30000; 

or

#define m 30000

Just note that in C const objects have external linkage by default, so to get the equivalent const declaration you have to use static const, not just const.

Also note that in C language const objects are not constants, but rather "constant variables". If you need a true constant (i.e. an entity that forms constant expressions), you have to use either #define or enum constant.

The latter is normally an issue with integral constants only. In your case of a double the approach with [static] const might work best.