Hi Durga,
I would like to provide some inputs regarding the implementation of employee codes.
The employee code system has to be decided on the basis of the increase in the number of employees you are expecting in the company and also based on the hierarchy of your company and as suggested by dashrat region wise/department wise and hence should be implemented in such a manner wherein having a look at the employee code the senior management would be able to determine what position he works in, where he is located or which department he works for and the number of years he has been working with the company.
Alphabets can be used to define values for each of the above and a reference file maintained with the HR.
Thanks & Regards,
AJ