Quick A: default constructors are called if available, otherwise there is no initialisation.
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In lieu of explicit initialization, initialization of members in classes works identically to initialization of local variables in functions.
For objects, their default constructor is called. For example, for std::string, the default constructor sets it to an empty string. If the object's class does not have a default constructor, it will be a compile error if you do not explicitly initialize it.
For primitive types (pointers, ints, etc), they are not initialized -- they contain whatever arbitrary junk happened to be at that memory location previously.
For references (e.g. std::string&), it is illegal not to initialize them, and your compiler will complain and refuse to compile such code. References must always be initialized.
So, in your specific case, if they are not explicitly initialized:int *ptr; // Contains junk string name; // Empty string string *pname; // Contains junk string &rname; // Compile error const string &crname; // Compile error int age; // Contains junk