1 Intro C++

Question 1

Main()

Answer 1

• not part of any class, is a function NOT a method because of this
• must be global
• return type int, return 0 always

Question 2

include

Answer 2

Compiler inserts the contents of the file “something” in the place where the #include statement appears

Question 3

Functions vs methods

Answer 3

functions are outside of a class

Question 4

Forward declarations

Answer 4

declaring a function before you implement it, so you can use it in earlier functions/methods

Question 5

Syntax for making a class?

Answer 5

class className {};

**note ; after class declaration

Question 6

Syntax for making a constructor?

Answer 6

className::className() {
//create variablels n stuff
}

** notice NO return type

Question 7

Where do you define a class? Implement aa class?

Answer 7

1. Header file!

2. .cpp file

Question 8

What should a header file contain?

Answer 8

• Appropriate preprocessor directives
• class declaration
• public and private methods declaration

Question 9

What should a class’s .cpp file contain?

Answer 9

• # include it’s header file

- initialize all methods of the class

Question 10

Straight up meaning of

#include
#ifndef
#endif
#define

Answer 10

#include = direct copy of file specified to location of this
#ifndef = "if not defined"
#endif = the end of any preprocessing ifs
#define = defines a macro... can make #define HOP 5

Question 11

What should you #include?

Answer 11

.h files

Question 12

#define FOO
#ifdef FOO   // is true!
// ...
#endif
#ifndef FOO  // is false!
// ...
#endif

Answer 12

Understand!

Question 13

include loops

Answer 13

never ending inclusion of two files

Question 14

odd.h:
#ifndef ODD_H
#define ODD_H
#include "even.h"
bool odd (int x);
#endif
even.h:
#ifndef EVEN_H
#define EVEN_H
#include "odd.h"
bool even (int x);
#endif

Answer 14

odd.h:
#ifndef ODD_H        1
#define ODD_H        2
#include "even.h"        3
bool odd (int x);           9
#endif                     10

even.h:
#ifndef EVEN_H         4
#define EVEN_H          5
#include "odd.h"           6 
(already defined  so nothing occurs)
bool even (int x);             7 
#endif                   8

Question 15

Whats a pointer?

Answer 15

a type of variable which stores a memory address of another object… instead of a number or a character

Question 16

How to make a pointer?

Answer 16

int x;
chary;
poopy *poopyhead;

Question 17

Two meanings of a *?

Answer 17

Definition: defines type as pointer “int *x;”

Expression: dereferences a pointer… so *x will go to the object pointed at

Question 18

Two meanings of a &?

Answer 18

Definition: makes a reference

Expression: address of x

Question 19

int x =1;

make a pointer that points to x

Answer 19

int *x_pointer = &x;

Question 20

int n =30;
int * p;
*p =n;

Walk through this code. Where does the error occur?

Answer 20

integer n created.
Pointer p initalized.
Value at p tried to set to n. ERROR

Error occurs because *p dereferences p, but p doesn’t have anything to dereference… so its just confused.

Question 21

int n =30;
int * p;
*p =n;

Way to fix this?

Answer 21

int n =30;
int * p = NULL;
*p =n;

this way *p can be followed to NULL at least

Question 22

What is static memory allocation? Make an aarray with static memory allocation.

Answer 22

-amount of space is already known when initalized

int someArray[10];

Question 23

Dynamic memory allocation uses what keyword?

Answer 23

new

Question 24

Make an array of ints with dynamic memory allocation

Answer 24

int *ages = new int[];

Question 25

Dynamic memory allocation necessities?

Answer 25

delete it t the end!

Clears up memory, allows those spaces to be used, but doesn’t delete them yet!

Question 26

int * ages = new int[];

How to delete a ages?

Answer 26

delete [] ages;

Question 27

Accessing age from person object or reference?

Answer 27

Use person.age

Question 28

Acessing age from person pointer

Answer 28

Use person -> age

or

(*person).age

Question 29

Make it so List and ListItr can access  private data from Listnode
class ListNode {

public:
ListNode(); // Constructor

private:
int value;
ListNode *next, *previous; // for doubly linked lists
};

Answer 29

class ListNode {

public:
ListNode(); // Constructor

private:
int value;
ListNode *next, *previous; // for doubly linked lists

    friend class List;
    friend class ListItr;
};

Question 30

char* x, y;
vs
char *x,y;

Answer 30

• is right assoocited, meaning that *x,y will be two pointers.
• x,y will be a pointer and a char

Question 31

Assume int is 4 bytes

how much storage does x hold?

x=new int[10];

Answer 31

40 bytes throughout the life of x.

Question 32

Why is dynamic memory allocation not efficient at storing data?

Answer 32

allocates more space than needed between elements!

Question 33

References are similar to pointers how?

Answer 33

they both hold memory addresses

Question 34

Pointer vs reference

Answer 34

1. A reference cannot change. The address assigned to the variable cannot change to another address.
2. It must be initialized upon declaration (cannot just use NULL)
3. Has implicit dereferencing! Nice feature

Question 35

class example1 {
  public:
    int *a;
};

int main() {
  example1 *c = new example1;
  int x = 0;
  (*c).a = &x; // assign address of x
  c->a = &x; // defrerence c, then access a
}

Answer 35

This makes sense.

Question 36

How to pass a parameter by value?

Answer 36

int max(int a, int b);
int swap(int *x, int *y);
bool compare(Rational left);

Question 37

How to pass a parameter by reference?

Answer 37

void swap(int &x, int&y);

Question 38

When to use pass by reference?

Answer 38

When you want the ‘formal parameter’ (or the parameter as it appears in the prototype of the functions) to CHANGE the value of the actual arguments

Question 39

When to use a call by constant reference?

Answer 39

When you DONT want the formal parameter to change!

Question 40

C++ default methods

Answer 40

• default constructor(no parameters, doesn’t do anything at all)
• copy constructor (constructor that creates a new object, and initialized copy of the same type of object)
• destructor (~, frees up resources)
• operator=() (copy assignment operator…. makes one object already constructed copied into the other object already constructed… an operator override

Question 41

Go through column 13 on deck 1! Sample code!

Answer 41

yeah!

Question 42

Copy constructor vs assignment operator

Answer 42

copy constructor = new object is created from an existing object

assignment operator = already initalized object is assigned a new value from another object