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Sample Technical Questions

C Sample Question

41. #include‹stdio.h›
    main()
    {
    struct xx
     {
    	  int x;
    	  struct yy
    	   {
    	     char s;
    	     struct xx *p;
    	   };
                	 struct yy *q;
               	 };
              	}

    Answer:

    Compiler Error

    Explanation:

    in the end of nested structure yy a member have to be declared.

42. main()
    {
     extern int i;
     i=20;
     printf("%d",sizeof(i));
    }

    Answer:

    Linker error: undefined symbol '_i'.

    Explanation:

    extern declaration specifies that the variable i is defined somewhere else. The compiler passes the external variable to be resolved by the linker. So compiler doesn't find an error. During linking the linker searches for the definition of i. Since it is not found the linker flags an error.

43. main()
    {
    printf("%d", out);
    }
    int out=100;

    Answer:

    Compiler error: undefined symbol out in function main.

    Explanation:

    The rule is that a variable is available for use from the point of declaration. Even though a is a global variable, it is not available for main. Hence an error.

44. main()
    {
     extern out;
     printf("%d", out);
    }
     int out=100;

    Answer:

    100

    Explanation:

    This is the correct way of writing the previous program.

45. main()
    {
     show();
    }
    void show()
    {
     printf("I'm the greatest");
    }

    Answer:

    Compier error: Type mismatch in redeclaration of show.

    Explanation:

    When the compiler sees the function show it doesn't know anything about it. So the default return type (ie, int) is assumed. But when compiler sees the actual definition of show mismatch occurs since it is declared as void. Hence the error.
    The solutions are as follows:

    1. declare void show() in main() .
    2. define show() before main().
    3. declare extern void show() before the use of show().

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