What are built-in function

Question

those function which are predefined in the program

Answer 1

Predefined functions are functions that are built into C++ Language to perform some standard operations. The functions that are stand alone used for general purposes and that are not depended on any classes are stored in the Standard Function Library. Predefined functions in the Standard Function Library are listed based on different categories.
List of basic types of standard library functions:
I/O Functions.
String and Character Functions
Mathematical Functions
Time,Date and Localization Functions.
Dynamic Allocation Function
Utility Functions