C Preprocessor - C Programming Questions and Answers

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What will be the output of the program?

 #include
 #define str(x) #x 
 #define Xstr(x) str(x)
 #define oper multiply 

 int main()
  {   
     char *opername = Xstr(oper);     
     printf("%s\n", opername);     
     return 0;
  }

Error: in macro substitution

Error: invalid reference 'x' in macro

print 'multiply'

No output

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Answer : Option C

Explanation :

The macro #define str(x) #x replaces the symbol 'str(x)' with 'x'.

The macro #define Xstr(x) str(x) replaces the symbol 'Xstr(x)' with 'str(x)'.

The macro #define oper multiply replaces the symbol 'oper' with 'multiply'.

Step 1: char *opername = Xstr(oper); The varible *opername is declared as an pointer to a character type.

=> Xstr(oper); becomes,

=> Xstr(multiply);

=> str(multiply)

=> char *opername = multiply

Step 2: printf("%s\n", opername); It prints the value of variable opername.