External environment refers to the major factors and forces outside the organization that have the potential to significantly affect the performance of an organization. External environment is divided into two parts i.e. mega environment or general environment and specific or task environment.
_tcscat is a C function, to concatenate C-style strings; CString is a class (which has built in concatenation via operator+), not a C-style string.
In C++, function prototype is a declaration of function without its body to give compiler information about user-defined function. Function prototype in the above example is: int add(int, int);