Naming: Why should named constants be all uppercase in C++/Java?

Question

I know, that for C++ and Java it is a well established naming convention, that constants should be written all uppercase, with underscores to separate words. Like this (Java

Answer 1

I can imagine that initially, back in the C days, people would implement "constants" symbolically, using the pre-processor:

typedef unsigned int Color;
#define BACKGROUND_COLOR 0xffffff

Such "constants" are just prettified literals, and as such they don't behave quite as variables. You can't, for example, take the adress of such a "constant":

Color *p = &BACKGROUND_COLOR; // Breaks!

For this reason, it makes sense to have them "stand out", as they're really not just "variables you can't change".