Types in C++

Question 1

Is C++ statically typed?

Answer 1

Yes

Question 2

What does it mean for a lanuage to be statically typed?

Answer 2

Every variable, function argument and function return must be labeled with a type so the compiler knows how much memory to allocate, what type of values to store, what operations can be performed and how to interpret the bit patterns associated with the value.

Question 3

What are the two catagories for types in C++?

Answer 3

Fundamental (built-in) types and derived (compound) types

Question 4

List C++ built in types

Answer 4

Booleans (bool), Characters (char), Integers (int), Floating Point (float), Double Precision Floating Point (double), Valueless (void), Wide Char (wchar_t), std::nullptr_t

Question 5

List C++ built-in type specifiers

Answer 5

short, long, signed, unsigned.

Question 6

Where are type specifiers placed?

Answer 6

Before the type (unsigned int, for example)

Question 7

What typical sizes are available for the int built-in type?

Answer 7

short int (16-bit), int (32-bit) long int (64-bit) - except windows which keeps it at 32-bit

Question 8

Name the built-in integral types

Answer 8

int and char

Question 9

What sizes are available to a char?

Answer 9

One byte (typically 8 bits, but not on all systems)

Question 10

At Google, what can we assume about the sizes of ints and chars?

Answer 10

The char is 8-bits and the int is at least 32-bits. Within google3, we can assume a 32-bit int size with sizeof(int) = 4.

Question 11

What is the default signed-ness of an int?

Answer 11

Signed, it is not common to write signed int

Question 12

How does a signed int represent its numbers when it has N bits available?

Answer 12

Two’s compliment (-2^(N-1), 2^(N-1) - 1)

Question 13

How does an unsigned int represent its numbers when it has N bits avaible?

Answer 13

(0, 2^N - 1)

Question 14

Describe overflow behavior for signed and unsigned ints

Answer 14

For signed, it is unpredictable. For unsigned, it is predictable and acts similar to the modulo operator.

Question 15

Describe conversion behavior from signed to unsigned ints

Answer 15

It is well defined,

Question 16

What is the typical size of a bool?

Answer 16

One byte

Question 17

What is the size of a char?

Answer 17

One byte

Question 18

Are chars signed or unsigned by default?

Answer 18

Neither, it is up to the implementation

Question 19

How large is a wchart_t

Answer 19

Typically 2 to 4 bytes

Question 20

What is the typical encoding of a char?

Answer 20

It is typically UTF8

Question 21

What is a void* pointer?

Answer 21

Universal pointers that can be point to any variable not declared as const or volatile.

Question 22

Are void pointers use in C++?

Answer 22

Yes but it is uncommon

Question 23

How do you dereference void *s?

Answer 23

Cast it to another type

Question 24

What is std:nullptr_t?

Answer 24

Is a built-in type with one value which is the null point literal nullptr

Question 25

Write a simple function in C++ to showcase its syntax

Answer 25

int MyFunc(int v) {return 1;}

Question 26

What is a member function? What is the difference between a static and non-static?

Answer 26

A member function is defined and associated with a class. A static function is associated with the class at large, while a non-static function is associated with an instance or object of the class

Question 27

Provide an example of passing a function pointer as an argument for a function

Answer 27

void TakesFunc(int (*)(int));
…
// The & here is optional. There is an implicit conversion (“decay”) from a
// function type to its corresponding function pointer type.
TakesFunc(&MyFunc);

Question 28

What is the type of a non-static member function?

Answer 28

It is the return type, the implicit this parameter from its class and the argument parameters -> int (Class::*) (int int)

Question 29

What is the type of static member functions and free member functions?

Answer 29

It is the return type and the argument parameters -> int (int, int)

Question 30

Show an example of how you create an array in C++

Answer 30

int array[5] = {1,2,3,4,5};
int array = {1,2,3,4,5};
int array[5] = {}

Question 31

How do you create a char array in C++?

Answer 31

char array[3] = {‘a’,’b’,’c’};
char array[3] = “abc”;

Question 32

Show how you can create a pointer.

Answer 32

Use the * after the type in the declaration. Use the & to reference the value (provide the address):
int* ptr = &value;

Question 33

When is the memory location of a variable set?

Answer 33

At runtime

Question 34

What is the size of a pointer?

Answer 34

It is architecture dependent. However, within an architecture, all pointers are typically the same size. 8 bytes for 64 bit architectures and 4 bytes for 32 bit.

Question 35

What is dereferencing and how do you do it?

Answer 35

Dereferencing is retrieving the value stored at an address associated with a pointer. Use the * operator (*ptr)

Question 36

What are references?

Answer 36

They act like aliases and allow one to refer to existing objects without explicitly dereferencing them (unlike pointers). They cannot be null and must be initialized.

Question 37

What are lvalue and rvalue references?

Answer 37

References that are assigned from the left or right side of an assignment operator respectively. & is used for lvalue (int& val = 1) and && used for rvalue (int&& val

Question 38

How can a user define their own types?

Answer 38

Through enums, classes, structs and unions.

Question 39

Compare and contrast structs and classes

Answer 39

Both contain member functions and data members. Members of structs are default public while members of classes are default private. Typically structs are used for simple code blocks without invariants classes for code with invariants (the state stored in the object does not change).

Question 40

Why should you use enum class over plain enum?

Answer 40

enum class is strongly-typed and scoped and prohibits direct comparison via integers making it safer then the upscoped plain enum.

Question 41

Show and example of how you could create an enum in c++?

Answer 41

enum class Color (red, blue, green}
Color color = Color::red;

Question 42

What are type aliases?

Answer 42

Allow you to refer to another type using an alias

using Bananas = int;
Bananas b = 5;

typedef int Bananas;
Bananas b = 5;