Question

Difference between user defined data type and built in data type

Answer 1

Built in Data types are those that a programming language natively supports e.g. int, float, char, double.
User Defined Data types are those that are structured by users i.e. programmers for the sake of convinience e.g. array, you don't have any data type in C where you can store a list of integer elements, other examples include queue, stack.