Preprocessing and preprocessing macros

// The system comes with preprocessing macros

#include<stdio.h>

void main() {
    

	//region It's equivalent to a label that can wrap him   There's no practical use 
#pragma region hong 
	printf("%s \n", __DATE__);// Get date 
	printf("%s \n", __TIME__);// Acquisition time 
	printf("%s \n", __FILE__);// Get the file name 
	printf("%d \n", __LINE__);// Print the current number of lines 
	printf("%d \n", __STDC_HOSTED__);// If you return 1 Is to meet the standard C library 
	//printf("%d \n", __STDC__)// If it's standard C The compiler can use this   If it's not, it will report an error 
	//printf("%d \n", __LP64__);//__LP64__  Judge whether the system is 64 position   If so, for 1
#pragma endregion hong
	system("pause");
}

// Macro definition

#pragma once // Prevent header files from repeatedly containing 
#include<stdio.h>

#define OOO 1 // Macro definition OOO by 1
#undef OOO // Undefine macro 

void main() {
    
#ifdef OOO
	printf("0"); // If there is a macro definition, it returns true 
#else
	printf("-1 \n"); // Print without -1
#endif // OOO


#ifndef OOO // If there is no definition, it returns true 
	printf("0");   // If there is a macro definition print 0
#else
	printf("-1"); // Print without -1
#endif // OOO


#if OOO

#else

#endif

	system("pause");
}