Question

Difference between user defined and system defined functions in c

Answer 1

If I understand your request correctly, you are asking about the difference between standard and custom resources. A system-defined resource is one that is managed by the system. Standard objects and fields fall in this category. These resources can't be deleted and usually have severe limitations on how they may be modified (e.g. you cannot change their data type). Conversely, a user-defined resource is one that is created and managed by system administrators. Custom fields and objects are the most obvious examples of this, but also includes validation rules, workflow rules, custom tabs, and so on.