Why would someone use #define to define constants?

Question

It\'s simple question but why would someone use #define to define constants?

What\'s the difference between

#define sum 1 and const int su

Answer 1

const int is just an int that can't change. #define is a directive to the C preprocessor, which is much more than just for defining constants.

See here for more details: http://en.wikipedia.org/wiki/C_preprocessor