Yes. This can be done by using the #if, #else, and #endif preprocessor directives. For example, certain
compilers use different names for header files. One such case is between Borland C++, which uses the header file alloc.h, and Microsoft C++, which uses the header file malloc.h. Both of these headers serve the same purpose, and each contains roughly the same definitions. If, however, you are writing a program that is to support Borland C++ and Microsoft C++, you must define which header to include at compile time. The following example shows how this can be done:


#ifdef _ _BORLANDC_ _
#include <alloc.h>
#else
#include <malloc.h>
#endif

No, we cannot do so since #include's are processed at preprocessor stage, not on compile time. But we can avoid the inclusion of header files by using #ifdef, #ifndef etc.

Can you define which header file to include at compile time?

Yes. This can be done by using the #if, #else, and #endif preprocessor directives. For example, certain
compilers use different names for header files. One such case is between Borland C++, which uses the header file alloc.h, and Microsoft C++, which uses the header file malloc.h. Both of these headers serve the same purpose, and each contains roughly the same definitions. If, however, you are writing a program that is to support Borland C++ and Microsoft C++, you must define which header to include at compile time. The following example shows how this can be done:


#ifdef _ _BORLANDC_ _
#include <alloc.h>
#else
#include <malloc.h>
#endif



--------------------------------------------------------------------------------

No, we cannot do so since #include's are processed at preprocessor stage, not on compile time. But we can avoid the inclusion of header files by using #ifdef, #ifndef etc.

Yes. This can be done by using the #if, #else, and #endif preprocessor directives. For example, certain
compilers use different names for header files. One such case is between Borland C++, which uses the header file alloc.h, and Microsoft C++, which uses the header file malloc.h. Both of these headers serve the same purpose, and each contains roughly the same definitions. If, however, you are writing a program that is to support Borland C++ and Microsoft C++, you must define which header to include at compile time. The following example shows how this can be done:


#ifdef _ _BORLANDC_ _
#include <alloc.h>
#else
#include <malloc.h>
#endif


No, we cannot do so since #include's are processed at preprocessor stage, not on compile time. But we can avoid the inclusion of header files by using #ifdef, #ifndef etc.

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