What is the use of const keyword in functions?

[Natsu6767]

I have seen a lot of examples where const is used instead of only declaring a constant variable.....so how does the const keyword function there.
For example:

 virtual const char* what() const
{}

also:

void print(const int n) {}

what happens in the above codes if const is not used and what is the effect produced due to the usage of const keyword?

[coder777]

The use of const is always the same: The const object cannot be modified [without tricks like const_cast or mutable]

mutable:
http://en.cppreference.com/w/cpp/keyword/mutable


const_cast:
http://en.cppreference.com/w/cpp/language/const_cast


In case of a function, const can only be used with a member function. In that case the const prevents the modification of the member variables of this object.

[48T7M4Gy]

const means constant, can't be changed, read-only