C++ Object-Oriented Interview Questions And Answers - What is a modifier? or What is an accessor?

What is a modifier? 

A modifier, also called a modifying function is a member function that changes the value of  at least one data member. In other words, an operation that modifies the state of an object. Modifiers are also known as ‘mutators’. Example: The function mod is a modifier in the following code snippet:

class test
{
int x,y;
public:
test()
{
x=0; y=0;
}
void mod()
{
x=10;
y=15;
}
};

What is an accessor? 
An accessor is a class operation that does not modify the state of an object. The accessor functions need to be declared as const operations