Some data are fixed and not change such as Date of Birth (DOB), Gender, Blood group Some data may change but not often such as name, address, marriage status. Some data may always change such asAGE. We don’t record the data that always change because it need to be update frequently in order to make it up to date. AGE is not generally recorded. To know the age of person we can simply be calculated by the date of birth of person deducted from the current date.