C Programming - C Preprocessor - Discussion

Why not A?

Why its answer is c?

Before Explanation of all the options, need to know that, in Macro definition(#define CUBE(X) (X*X*X)), there are Macro Expansion and Macro Templates.

In given Question, #define CUBE(X) (X*X*X) is Macro definition, CUBE(X) is Macro-Templates and (X*X*X)is Macro-Expansion.

A. Macro-Expansion must not followed by semicolon(;)
B. In Macro-Expansion and Macro-Templates using different variables(i.e x and X)
C. Correct Answer according to Macro definition.
D. Wrong, because only parenthesis i.e () is allowed in Macro-Expansion.

Thank You.

Here OPTION A is correct in some cases but other options are absolutely wrong.....given below is example for the answer.
According to statements written in main.
for example
1. #define CUBE(X) (X*X*X);
this will be correct when we have statement like
main
{
int a;
a=CUBE(a) //this will be replaced by (a*a*a); along with semicolon // which is syntactically correct
}

BUT C IS NOT CORRECT AS SPACE IS NOT GIVEN.

Yes, @Neeraj is right.

IN GCC compiler, both B, C answer is correct.

BOTH A and C options are correct.

WE CAN USE SEMICOLON IN #DEFINE try it by urself like,

#define mul(x) (x*x*x)
main()
{
int a;
a=mul(5)
}
IN THIS CASE IT WILL RUN WITH NO ERROR AND WITH CORRECT OUTPUT

BUT
#define mul(x) (x*x*x)
main()
{
printf("%d", mul(5));
}
Will give an error as in printf semicolon cn not be used with a variable.

And space or no space it doesn't matter.

#define mul(x) (x*x)
Is same as
#define mul(x)(x*x)

How could option C be correct? There is no space between CUBE(X) and (X*X*X). Please someone explain it.

As per my knowledge;

a) it contain a semicolon.
b) in function it contains at a time lower and upper case letters.
c) it does not contain at least one space.
d) it contains curly braces.

Depends on the usage in the main method. All are correct except for B which makes no sense as the lower case is used.

A and B are not work because a option is semicolon and option B gives the small latter x.