学习笔记（79):C语言入门到精通-预处理器-下

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#include <stdio.h>

#define MY
#define XX

// #undef, #if, #else, #elif, #endif
int main() {

#ifdef MY
	printf("define MY\n");
#else
	printf("not define MY\n");
#endif

#undef MY  // 去掉定义，使之没有定义

#ifdef MY
	printf("define MY\n");
#else
	printf("not define MY\n");
#endif

#if (3 - 3)
	printf("if 1\n");
#elif 3 - 3 == 0
	printf("if 0\n");
#endif

	return 0;
}