> The program has been coded by a object oriented way which can easily tweaked
Neither of these things are true, in any shape or form.
You might have named them ".cpp" files, but apart from using cout, there is precious little C++ code here. There certainly isn't any use of classes or data abstraction which would make the "oo way" feasible.
First, you should learn the concept of passing parameters and returning results. Then you would be able to get rid of the stupid number of global variables you have.
Second - remove all those label: .. goto loops you have, and replace them with proper while loops.
Why? What point is there in frustrating the user even more by forcing pointless wait loops.
gotoxy(27, 4); cout<<"Wrong date entered--WAIT";
4. #include "func.cpp" //Contains all the User-Defined functions accessed in the program
What you should have is a func.h and func.cpp being compiled separately.
You just about get away with it with only a couple of files, but when you get to writing programs with 10's (or 1000's) of source files, you need a different approach!
5. > void main() //using void to cut the crap
Yeah - riiiigggghhhhtttttt