Question

C++ What does it mean when you pass by reference a function? Example:

int & modify(){}

same question with pointers. Example:

int * modify(){}

Answer 1

Alias:

Alias means another name of an existing variable. In C++, the reference variable is an alias.

For example:

int x;

int &y = x;

In the above statement, 'y' is an alias of variable 'x'.

Pass By Reference

When we pass the parameter as a reference, then the reference of the parameter is passed to the called function. The reference variable uses the pointer for implementation. A reference is the same object but a different name and it can't be assigned null. A reference variable can be used directly and there is no need for dereferencing operator '*'.

For example:

//method to return the reference of a variable
int & modify()
{   
return a;
}

In the above method, we return the reference of a variable.

When we want to make changes in the actual parameter then we should use the reference variable.

By using pointer:

int * modify()

{

}

In the above example, the address is return and we need the dereferenced operator to get the value.

Difference between pointer and reference:

• A pointer hold the address of a variable but a reference is an alias name of a variable.
• There is no need of a dereferenced operator for a reference variable.
• On a pointer, we can use an increment operator but on the reference variable, we can't use it.