C++ Fundamentals Including C++ 17

Question 1

What does “shortcutting” refer to for the && and || operators?

Answer 1

If the result can be determined after evaluating only the first argument, the second will not be evaluated. (Related Clip: Comparisons)

Question 2

A member function should be marked as const…

Answer 2

… when you first write it, unless it changes a member variable. (Related Clip: Member Functions)

Question 3

Who makes the decision about adding new features to the C++ language?

Answer 3

An International Standards Organization committee. (Related Clip: Standardization)

Question 4

Which of these statements about references and polymorphism is correct?

• Only const references are polymorphic.
• References support polymorphism more strongly than pointers do.
• References do not support polymorphism.
• References support polymorphism in the same way as pointers.

Answer 4

-References support polymorphism in the same way as pointers. (Related Clip: References and Inheritance)

Question 5

What does the break statement mean in a while loop?

Answer 5

Control should exit the loop and continue after it. (Related Clip: While)

Question 6

What does this line of code do?

std::cout &laquo_space;“Type your name” &laquo_space;std::endl;

Answer 6

Prints “Type your name” (without the quotes) on the screen and moves the cursor down one line. (Related Clip: Demo: Visual Studio Hello World)

Question 7

Why would any programmer create an object on the free store, also called the heap?

Answer 7

So that the memory can stay in scope after the creating function has ended. (Related Clip: The Free Store)

Question 8

When moving data of one type into a variable of another type, when do checks on the coversion validity occur?

Answer 8

When your code is compiled. (Related Clip: Demo: Fundamental Types)

Question 9

If you want to be sure that a developer doesn’t forget to do something, such as closing a file or connection, how can you make sure it gets done?

Answer 9

Put the closing call into the destructor for a class representing the file or connection. (Related Clip: Scope)

Question 10

A template may count on the types you us it with to implement a particular member function or operator overload. Which technique will not help you to discover the constraints on your type?

• Reading documentation for the template
• Understanding the template error messages when you try to use it
• Reading the source code of the template
• Looking at the constraints in the declaration of the template.

Answer 10

-Looking at the constraints in the declaration of the template. (Related Clip: Template Specialization)

Question 11

If you declare a function but do not implement it, and code tries to call it, what kind of build error will occur?

Answer 11

Linker error. (Related Clip: Demo: Understanding Error Messages)

Question 12

After this loop, what is the value of y?

int y = 0;
for (int i = 0; i<5; i = i + 1)
{
   y = y + i;
}

Answer 12

10 (Related Clip: For)

Question 13

When your code relies on classes and functions in a namespace, the best way to minimize your typing while preserving your program’s intent is to:

• add using statements referring to the entire namespace, e.g. using namespace std;
• always type the full name including the namespace, e.g. std::cout , whenever referring to the name
• You should not use code form a different namespace
• add using statements referring to the specific name within the namespace, e.g. using std::cout;

Answer 13

-add using statements referring to the specific name within the namespace, e.g. using std::cout; (Related Clip: Demo: Namespaces)

Question 14

If you write a class with a virtual function in it, what other function should be marked as virtual?

Answer 14

The destructor (Related Clip: Demo: Indirection and Inheritance)

Question 15

If you delcare an integer pointer like this:

int const * p;

Then attempt to compile these two lines:

p = &something;
*p = 2;

Will they compile?

Answer 15

The first, which changes p, will. The second, which dereferences p, will not. (Related Clip: Const with Indirection)

Question 16

When you use a template function in your code, the work of stamping out the version of the function you need is done when?

Answer 16

at compile-and-link time. (Related Clip: Templates)

Question 17

Which of these is the correct sequence when constructing an object that is an instance of a derived class?

• The derived constructor runs and then the base constructor
• The base constructor runs and then the derived constructor.
• Only the derived constructor runs.
• All the initializers run and then the derived constructor.
• The derived constructor must call the base constructor to make it run.

Answer 17

-The base constructor runs and then the derived constructor. (Related Clip: Demo: Inheritance)

Question 18

Building in C++ involves compiling and linking. What is the difference between them?

Answer 18

Each source file is individually compiled and the results are linked together into a single output file. (Related Clip: Building)

Question 19

Templates allow you to write code once, and use it for any type, such as int, Employee, or Person. What important C++ feature do they retain while working across type?

Answer 19

Type safety (Related Clip: Template Classes)

Question 20

include

What does this line of code do?

Answer 20

Makes the string class in the Standard Library available to your code. (Related Clip: Introduction)

Question 21

How do you indicate that a C++ function, other than a constructor or destructor, is like a subroutine, not returning a value.

Answer 21

Use the return type of void. (Related Clip: Demo: Member Functions)

Question 22

If I delcare two integers like this:

int const a = 10;
const int b = 10;

In what way are a and b different in ther const-ness?

Answer 22

There is no difference other than style. (Related Clip: Const After or Before?)

Question 23

Two fo the three special functions referred to in the Rule of Three are the copy constructor and the copy assignment operator. For a class called Person these would be

Person::Person(Person const& p)

and

Person::operator=(Person const& p)

What is the third?

Answer 23

The destructor.

Person::~Person()

(Related Clip: Manual Memory Management)

Question 24

Which of these is a fundamental type in C++?

• date
• object
• string
• boolean

Answer 24

-boolean (Related Clip: Fundamental Types)

Question 25

How do your write a conditional expression that means “a and b are not equal”?

Answer 25

a != b

Related Clip: Comparisons

Question 26

Why would an operator overload for a class classed Date be a free function instead of a member function of the Date class?

Answer 26

It handles the case where something that is not a Date is on the left of the operator; e.g. 3 + tomorrow

(Related Clip: Writing an Overload)

Question 27

Which of these is not a difference between older enumerations (enum) and the new scoped enumerations (enum class) ?

• An enum member can be referred to by its name alone, but for an enum class you must use a full name including the name of the enum class.
• Two different scoped enumerations can have elements with the same name; names in an enum must be unique across all enums.
• The compiler can assign values to the members of an enum class but they must be provided for enums.
• The underlying data type of enum is always int but can be other types for an enum class

Answer 27

-The compiler can assign values to the members of an enum class but they must be provided for enums.
(Related Clip: Enumerations)

Question 28

When you use dynamic_cast<> to cast something to an incompatible type, what happens?

Answer 28

it returns nullptr (Related Clip: Casting and Indirection)

Question 29

When a function takes a parameter by reference…

• The application will run more slowly
• The function is called a reference function and should also return a reference
• changes to that parameter in the function also change the value that was passed to it.
• it must always be a const reference to prevent compiler errors.

Answer 29

-changes to that parameter in the function also change the value that was passed to it. (Related Clip: Free Functions)

Question 30

Which of these is not a keyword that is part of a switch construct?

• default
• case
• break
• select

Answer 30

-select (Related Clip: Switch)

Question 31

A memory leak occurs when…

Answer 31

-memory has been allocated with new, but no pointer to that memory is in scope to use with delete. (Related Clip: Manual Memory Management)

Question 32

Describe what is Liskov substitutibility? Give an example.

Answer 32

The ability for functions to work with objects passed by reference that are not instances of the required type, but instead are instances that are derived from a base class of that required type. The “is a” relationship is respected.

Suppose tweeter.h is derived from Person.h, a function that accepts a Person instance passed by reference can still accept a tweeter instance and access the Person methods in the base class. (Related Clip: References and Inheritance)