Question

All built-in function prototypes are stored inside_______________

Answer 1

The answer is header files.
 
A function prototype gives details about the name of the function along with the number of operands used, the data types of its parameters and its return data type. In other words, it does not actually give details of how the function performs, the function prototype only specifies the data type of the result of the function and the data types of the parameters used in the function.
 
All built-in header function prototypes are stored inside header files. These header files are in turn specified in the #include directives.

Answer 2

All built-in function prototypes are stored inside header file.