C Programming - C Preprocessor
Exercise : C Preprocessor - True / False Questions
If the file to be included doesn't exist, the preprocessor flashes an error message.
Preprocessor directive #undef can be used only on a macro that has been #define earlier
There exists a way to prevent the same file from getting #included twice in the same program.
True, We can prevent the same file from getting included again by using a preprocessor directive called #ifndef (short for "if not defined") to determine whether we've already defined a preprocessor symbol called XSTRING_H. If we have already defined this symbol, the compiler will ignore the rest of the file until it sees a #endif (which in this case is at the end of the file).
#define XSTRING_H defines the same preprocessor symbol,
Finally, the last line of the file, #endif
A preprocessor directive is a message from programmer to the preprocessor.
Macro calls and function calls work exactly similarly.