Quick Reference

Declare a variable:

[DATATYPE] [VARIABLENAME];

int myNumber;

string myString;

float myFloat;

Declare a variable and initialize it:

[DATATYPE] [VARIABLENAME] = [VALUE];

int myNumber = 10;

string myString = "Hello!";

float myFloat = 9.99;

char myChar = 'a';

bool myBool = true;

Declare a named constant it:

const [DATATYPE] [NAME] = [VALUE];

const int NUMBER = 10;

const string STRING = "Hello!";

const float FLOAT = 9.99;

const char CHAR = 'a';

const bool BOOL = true;

Assign a value to a variable that has already been declared:

[VARIABLENAME] = [VALUE];

myNumber = 100;

Output text to the console:

cout << [ITEM];

cout << "Text";

cout << myVariable;

cout << "Label: " << myVariable << endl;

Get input from the keyboard and store it in a variable:

cin >> [VARIABLENAME];

cin >> myInteger;

cin >> myString;

Get a full line of text (with spaces) and store in a variable (string only):

getline( cin, [VARIABLENAME] );

getline( cin, myString );

Note that if you have a cin >> statement immediately before the getline statement, your input will get skipped. Instead, you need to add a cin.ignore() statement:

cin >> myNumber;
cin.ignore();
getline( cin, myString );

If statement:

If the condition evaluates to true, then execute the code within the if statement. Otherwise, skip that code completely.

if ( CONDITION )

if ( a == 1 )
{
}

If/Else statement:

If the condition from if statement results to false, then the code in the else case is executed instead. No condition is written with the else case.

if ( CONDITION )
else

if ( a == 1 )
{
}
else
{
}

If/Else if statement:

if ( CONDITION )
else if ( CONDITION )

if ( a == 1 )
{
}
else if ( a == 2 )
{
}

If/Else if/Else statement:

if ( CONDITION )
else if ( CONDITION )
else

if ( a == 1 )
{
}
else if ( a == 2 )
{
}
else
{
}

Switching based on a variable value:

switch( VARIABLE ) {
  case VALUE:
  break;
}

switch( myNumber )
{
    case 1:
    cout << "It's one!" << endl;
    break;
    
    case 2:
    cout << "It's two!" << endl;
    break;
    
    default:
    cout << "I don't know what it is!" << endl;
}

Loops

Looping with While Loops

Runs 0 or more times, depending on whether the CONDITION is true.

while ( CONDITION )
{
  CODE THAT CONTINUES RUNNING
}

while ( a < b )
{
    cout << a << endl;
    a++;
}

Looping with Do...While Loops

Runs at least once and then continues looping if the condition is true.

do
{
  CODE THAT CONTINUES RUNNING
} while ( CONDITION );

do {
    cout << "Enter a number: ";
    cin >> input;
} while ( input < 0 || input > max );

Looping with For Loops

Iterate some amount of times through the loop based on your counter variable and range.

for ( INITIALIZATION; CONDITION; UPDATE )
{
  // Do this multiple times
}

for ( int i = 0; i < 10; i++ )
{
    cout << i << endl;
}

Looping with Range-based For Loops

Iterates over all elements in a collection. Only moves forward, doesn't give access to index.

for ( INITIALIZATION : RANGE )
{
  // Do this multiple times
}

vector<int> myVec = { 1, 2, 3, 4 };
for ( int element : myVec )
{
    cout << element << endl;
}

Arrays

Declare array (traditional)

When declaring a vanilla array, you need to set its size. You can either hard-code the size with a number:

string arr[10];

const int TOTAL_STUDENTS;
string students[TOTAL_STUDENTS];

string cats[] = { "Kabe", "Luna", "Pixel", "Korra" };

Declare array (array object)

Remember that you will need #include <array> at the top of your file to use the array object.

Declare an array object, passing in what the data type of it values are, and the size of the array:

array<float, 3> bankBalances;

You can then use the array's size function to get the size of the array.

Iterate over a traditional array

Use a for loop to easily iterate over an array.

const int TOTAL_STUDENTS = 10;
string students[TOTAL_STUDENTS];

for ( int i = 0; i < TOTAL_STUDENTS; i++ )
{
    cout << "Enter name for student " << i << ": ";
    cin >> students[i];
}

Iterate over an object array

Use a for loop to easily iterate over an array.

array<string,10> students;

for ( int i = 0; i < students.size(); i++ )
{
    cout << "Enter name for student " << i << ": ";
    cin >> students[i];
}

File I/O

Create an output file and write

ofstream output;
output.open( "file.txt" );

// Write to text file
output << "Hello, world!" << endl;

Create an input file and read

ifstream input;
input.open( "file.txt" );
if ( input.fail() )
{
  cout << "ERROR: could not load file.txt!" << endl;
}
string buffer;

// read a word
input >> buffer;

// read a line
getline( input, buffer ); 

Functions

Prevent file duplication

When creating .h/.hpp files, it is important to include these lines to prevent file duplication, which happens if you #include this file in more than one place.

#ifndef _FILENAME_HPP
#define _FILENAME_HPP

// Code goes here

#endif

Function declaration

A function declaration contains the function header and no body. It declares that the function exists and will be defined elseware.

RETURNTYPE FUNCTIONNAME( PARAMETERS );

void DisplayMenu();

int Sum(int a, int b);

Function definition

A function definition defines how the function operates. It includes the function header and a function body, which has commands in it.

RETURNTYPE FUNCTIONNAME( PARAMETERS )
{
}

void DisplayMenu()
{
    cout << "1. Deposit" << endl;
    cout << "2. Withdraw" << endl;
    cout << "3. Quit" << endl;
}

int Sum(int a, int b)
{
    return a + b;
}

Calling a function

Calling a function requires invoking the function's name and passing in any arguments.

FUNCTIONAME( ARGS );

DisplayMenu();

int result = Sum( 1, 2 );

int num1 = 2;
int num2 = 5;
int result = Sum( num1, num2 );

Classes

Declaring a class

class CLASSNAME
{
    public:
    // Public members
    
    protected:
    // Protected members
    
    private:
    // Private members
};
// Don't forget ; at end of class block

Declare a class function

The class' function declaration goes within the class declaration in the .h/.hpp file:

class Example
{
    public:
    void Setup( int a, float b );
    
    private:
    int     m_a;
    float   m_b;
}

Define a class function

The class' function definition goes in the .cpp file:

void Example::Setup( int a, float b )
{
    m_a = a;
    m_b = b;
}

Getters and Setters

Getter functions:

• Don't take in any input data (no parameters).
• Return the value of a private member variable (has a return).

string Player::GetName()
{
    return m_name;
}

Setter functions:

• Take in an input value of the new data to be stored (has a parameter).
• Doesn't return any data (no return).

void Player::SetName( string newName )
{
    m_name = newName;
}

Pointers

Declare a pointer

DATATYPE* ptrname = nullptr;

int* ptrInt = nullptr;

string* ptrString = nullptr;

Assign an address to a pointer

Pointer variables store addresses as their values. To get the address of a variable, you use the address-of operator &.

ptrname = &variable;

int myInteger = 5;
int* ptrInt = nullptr;
ptrInt = &myInteger;

Dereference a pointer

A pointer stores an address, and dereferencing that pointer gives you the value of the item being pointed to.

*ptrname

cout << *ptrname;

cin >> *ptrname;

Check if pointer is pointing to an address

You will need to use an if statement to check if the pointer is pointing to nullptr or not. nullptr is an invalid address, so we assume the address is valid if it's not nullptr.

if ( ptrname != nullptr )

Memory management

Allocate memory for a single variable

DATATYPE* ptrname = new DATATYPE;

int * num = new int;

Node* newNode = new Node;

Deallocate memory of a single variable

DELETE ptrname;

delete num;

delete newNode;

Allocate memory for an array

DATATYPE* ptrname = new DATATYPE[ SIZE ];

int * numList = new int[ 100 ];

Node* nodeList = new Node[ 20 ];

Deallocate memory of an array

DELETE [ ] ptrname;

delete [] numList;

delete [] nodeList;