Passing parameters by reference in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to pass a parameter by reference in C++?

Passing a parameter by reference means giving the function access to the original variable, not a copy. Changes inside the function affect the original variable.

beginner

How do you declare a function parameter to be passed by reference in C++?

You add an ampersand (&) after the type in the function parameter list. For example: void func(int &x) means x is passed by reference.

beginner

What is the difference between passing by value and passing by reference?

Passing by value sends a copy of the variable, so changes inside the function do not affect the original. Passing by reference sends the actual variable, so changes affect the original.

intermediate

Can you pass a constant reference? Why would you do that?

Yes, by using <code>const Type &</code>. It allows the function to access the original variable without copying it, but prevents the function from changing it. This is efficient and safe.

intermediate

What happens if you try to pass a literal (like 5) to a function expecting a non-const reference parameter?

It causes a compilation error because literals cannot be bound to non-const references. Only variables can be passed by non-const reference.

How do you declare a function parameter to be passed by reference in C++?

A Use the keyword 'ref' before the type

B Add an ampersand (&) after the type

C Add an asterisk (*) after the type

D Use the keyword 'pointer' before the type

In C++, adding an ampersand (&) after the type declares a reference parameter.

What is the main advantage of passing parameters by reference?

A It makes a copy of the variable for safety

B It prevents the function from accessing the variable

C It allows the function to modify the original variable

D It slows down the program

Passing by reference lets the function change the original variable directly.

Which of these will cause a compilation error?

A Passing a literal to a function expecting a non-const reference parameter

B Passing a variable to a function expecting a reference parameter

C Passing a variable to a function expecting a const reference parameter

D Passing a pointer to a function expecting a reference parameter

Literals cannot be passed to non-const reference parameters because they are not variables.

What does the following function signature mean? void update(int &num)

A num is passed by value

B num is a constant

C num is a pointer

D num is passed by reference

The ampersand (&) means num is passed by reference.

Why would you use a const reference parameter?

A To prevent copying large objects and avoid modification

B To allow the function to modify the argument

C To make a copy of the argument

D To pass a pointer instead

Const references avoid copying large objects and prevent the function from changing the argument.

Explain how passing parameters by reference works in C++ and why it might be useful.

Think about how the function can change the original variable.

Describe the difference between passing a parameter by value, by reference, and by const reference.

Consider what the function can do with the parameter and how it affects the original.