What are standard functions in computer programming?

Answer 1

A "standard function" is a function that has been specified within a standard, to be blunt.

The C specification does not specify the requirement for any functions. Instead, you have other specifications, like Posix and Win32, that describe which functions are considered "standard", and therefore unomittable, from libraries supporting those standards.

Some standard functions under C include printf() and scanf() (in the stdio.h header), malloc() and free() (under stdlib.h), and sin() and cos() (in the math.h header file).

C++, on the other hand, has standard functions that are part of the individual (and currently accumulating) C++ specifications.