The file containing the definitions of the member functions of class datetype is called the file.

Implementation file

Explanation:

In popular object oriented programming languages like C/C++, The implementation file (source file) of a class is used to hold the code implementaion of the method(s) of the class, this is helpful for seperating interface and method implementation. When this seperation exists, header files will be used to declare all the methods and fields of the class.

In this way, the implementaion file will hold the actual source code of the methods that are declared in the header file and will have a line to include its associated header file. A major advantage of seperating code in this way is the enhancement of better code organization and code re-use