Define "promise"

In other words, when the compiler starts building your code, no #define statements or anything like that is left. What is the point of #define in c++? How can i use #if inside #define in the c preprocessor?

Or #define var 5 or enum { var = 5 }; The question is if users can define new macros in a macro, not if they can use macros in macros. Mar 4, 2017#define simply substitutes a name with its value.

Furthermore, a #define 'd constant may be used in the preprocessor: Jun 18, 2012#define width 10 is a preprocessor directive that allows you to specify a name (width) and its replacement text (10). The #define directive is a preprocessor directive;

What's the difference in practice between the inline keyword and the #define preprocessor directive?