define

来自「C实现的MUD,对大家基本入门网络游戏很有帮助!」· 代码 · 共 8 行

the #define preprocessor command creates a macro that can be expanded later
on in the file.  For example, if you have the line:

#define apples oranges

Then every time the word 'apples' appears after that point, it will be
treated as if it were 'oranges'.