C Programming - MCQ Practice Questions

The preprocessor expands A to B in the first pass. In the second pass, it recognizes B as a macro and expands it to 5. Nested macro expansion is allowed and the final result is 5. The preprocessor performs multiple expansion passes as needed.

__VA_ARGS__ (C99 feature) represents all variable arguments after the required parameters. It can be empty if no extra arguments are provided. It must be used with '...' in the macro definition. C89/C90 don't support variadic macros.

The macro DOUBLE(5) expands to (2*(5)) = 10 at preprocessing time. Array declarations require compile-time constant expressions, and macro-expanded constants qualify. The array has 10 elements. This works because the macro creates a constant expression that the compiler can evaluate.

Without parentheses, SQUARE(5+3) expands to 5+3*5+3, which evaluates to 5+15+3=23 due to operator precedence, not (5+3)*(5+3)=64. This demonstrates why macro parameters need parentheses.

__VA_ARGS__ allows macros to accept a variable number of arguments. Example: #define PRINT(...) printf(__VA_ARGS__) enables flexible argument passing.

The # operator (stringification) converts the macro argument into a string literal. STR(Hello World) becomes "Hello World", which printf prints with quotes.

The ## operator (token pasting) concatenates tokens directly. CONCAT(var,1) produces var1 as the variable name, not a##b.

The #undef directive undefines the previously defined macro MAX (which was 100). Then MAX is redefined as 200. So printf will output 200. The #undef allows redefining macros without compilation errors.