>>i need to include the last update date and time of the record in the form of dd-mm-yyyy,hh:mm:ss(it has to be updated by th program automatically) and i don't really know how.

Just add another field called UpdateDateTime (or whatever you want to call it) to each record which would be time_t. When you write a record get the system's time using time() function from time.h and save it to the field along with all the other information. If you don't want to save the date/time as an integer then you can call localtime() that returns a string and save that, but it will take up alot more space in the file.