Question

What is the problem in my code? It does not compile..

   class FileNames
   {
        public:
           static char* dir;
           static char name[100];

           static void Init3D()
           {
            FileNames::dir = "C://3D//";
            FileNames::name = "abc";
           }
   };   

Answer 1

You cannot assign to an array, so FileNames::name = "abc" fails (char arr[4] = "abc" works, however, because this is a direct initialization, not assignment). Either use a char* here as well, or use strcpy to copy data to the array or better a std::string which avoids many of the downsides of raw strings.

Most importantly you need to define your static members somewhere at global scope, outside a function:
char FileNames::name[100];. At this time initialization syntax using = would be possible even with the array, but the string to be assigned needs to have the same length as the array.