The preprocessor ## operator concatenates macro arguments. For example:
#define paste(x,y) x ## y
The paste() macro takes two arguments and concatenates them into one. The whitespaces surrounding the ## operator as well as the ## symbol are removed in the concatenation process. In the following example, the paste() function-like macro concatenates the literal 1000 and the affix L thereby creating the constant 1000L.#define paste(x,y) x ## y#define LONG_MAX paste(1000,L) // LONG_MAX equals 1000L
