C #undef:
A macro value in C replaces a part of a program with a value already defined by #define directive. The #undef is a preprocessor directive which is used to undefine the value defined by #define.
Syntax:
#undef macro_Name
Example:
#include<stdio.h> #define e 2.718 #undef e void main() { printf("e :%f\n",e ); } |
Output
error: 'e' undeclared |
