error dynamic_cast in c++

[gammavn]

I meets some problem with downcast in c++ programming language.
Thus, I needs your help.
My program has 5 classes. They are Employee (abstract class),Salary:public Employee,Hourly:public Employee,Commission:public Employee and BasePlusCom:public Commission.
In main() function,I used vector<Employee*>employees[4];
Then I assigned values to employees.
........
And I used structural syntax BasePlusCom* ComPtr=dynamic_cast<BasePlusCom*>(employees);
.....
And when compiles this program, compiler produces a warning that:
"dynamic_cast" used on polymorphic type 'class Employee' with G/R; unpredictable behavior may result.
And when I change dynamic_cast to reinterpret_cast then program run, but it not work properly.
How does casting in C++ differ?

[ithelp]

dynamic_cast can be used only for polymorphic classes.

[Alex Edwards]

Post the code please. I can see a few ways around this but it might be better to have a sense of the intent of the program before making a suggestion.

[vijayan121]

you need to enable RTTI. (use compiler switches for this.)
either you have turned it off by using the switch /GR-
or you are using a fairly old version of the microsoft compiler.
turn it on with the compiler switch /GR
http://msdn.microsoft.com/en-us/library/we6hfdy0.aspx