Output of C Programs | Set 10

Predict the output of the below programs.

Difficulty Level: Rookie

Question 1

#include<stdio.h> int main() {    typedef int i;    i a = 0;       printf("%d", a);    getchar();    return 0; }

Output: 0
There is no problem with the program. It simply creates a user defined type i and creates a variable a of type i.

Question 2

#include<stdio.h> int main() {   typedef int *i;   int j = 10;   i *a = &j;      printf("%d", **a);   getchar();   return 0; }

Output: Compiler Error -> Initialization with incompatible pointer type.
The line typedef int *i makes i as type int *. So, the declaration of a means a is pointer to a pointer. The Error message may be different on different compilers.

Question 3

#include<stdio.h> int main() {   typedef static int *i;   int j;   i a = &j;      printf("%d", *a);   getchar();   return 0; }

Output: Compiler Error -> Multiple Storage classes for a.
In C, typedef is considered as a storage class. The Error message may be different on different compilers.

Please write comments if you find any of the answers/explanations incorrect, or you want to share more information about the topics discussed above.

References:
http://www.itee.uq.edu.au/~comp2303/Leslie_C_ref/C/SYNTAX/typedef.html
http://publib.boulder.ibm.com/infocenter/macxhelp/v6v81/index.jsp?topic=/com.ibm.vacpp6m.doc/language/ref/clrc03sc03.htm
http://msdn.microsoft.com/en-us/library/4x7sfztk.aspx