Data Types

Let’s start with the basics and review data types in C++.

Main Primitives #

int #

• 32 bits of data (usually but not always)
• represents a whole number between -2,147,483,648 and 2,147,483,647

int videoWidth = 1920;
int videoHeight = 1080;
int numVideoPixels = videoWidth * videoHeight;

• integers do not support decimal points

int numStudents = 17;
int studentsPerTeam = 4;
int numTeams = numStudents / studentsPerTeam;  // 4 not 4.25!

int leftoverStudents = numStudents % studentsPerTeam;  // 1 student without a team :(

unsigned int #

• the unsigned (no +/- sign) version of int, only positive numbers
• represents 0 and positive whole numbers up to 4,294,967,295

char #

• 8 bits of data
• represents a whole number between -128 and 127

char numStudents = 17;
char studentsPerTeam = 4;
char numTeams = numStudents / studentsPerTeam;  // 4 not 4.25!

• if we try to use a char to represent a larger number, we will end up with the wrong value but C++ will not flag an error!

char videoWidth = 1920;  // ?

unsigned char #

• the unsigned (no +/- sign) version of char, only positive numbers
• represents 0 and positive whole numbers up to 255
• often used to represent characters in a string, using the ASCII table for conversion

unsigned char H = 72;
unsigned char i = 'i';
cout << H << i << endl;

bool #

• 1 bit of data
• represents true or false, 0 or 1, “yes” or “no”, etc.
• we can use the keywords true and false to set a boolean value

bool isTheSkyBlue = true;
bool isThisBoring = false;

• we can also use numbers, where 0 evaluates to false and any other number evaluates to true

bool numStudents = 17;  // true
if (numStudents)
{
  cout << "Class is in session!" << endl;
}

bool numStudents = 17;
cout << "There are " << numStudents << " students in class" << endl;  // 1

float #

• 32 bits of data
• represents a decimal number with ~7 significant digits
• float is short for “floating point”, which means that the decimal point can move positions (e.g. we can represent 1.23456 and 123.456 with the same amount of memory)

float videoWidth = 1920;
float videoHeight = 1080;
float aspectRatio = videoWidth / videoHeight;  // 1.777778

Additional Primitives #

The following primitive types are not used as often but are still useful if we need to optimize and use less memory, or increase precision and use more memory.

short and unsigned short #

• 16 bits of data
• represents whole numbers between -32,768 and 32,767 (signed) or 0 and 65,535 (unsigned)

long and unsigned long #

• 64 bits of data
• represents whole numbers between -9M and 9M (signed) or 0 and 18M (unsigned)

double #

• 64 bits of data
• represents floating point numbers with ~15 significant digits

Strings #

Like in most programming languages, strings (sequences of characters) are a complex class type, but they have special rules and optimizations applied to them since they are used very often.

string name = "John Doe";

string objects have a variety of methods (class functions) we can use to access their properties.

string name;
if (name.empty())
{
  cout << "No name has been set, using default..." << endl;
  name = "John Doe";
}
cout << "Hello, " << name << endl;

We can iterate through a string to get the characters it is made up of.

string name = "John Doe";
cout << "Your name is: ";
for (int i = 0; i < name.size(); i++)
{
  cout << name.at(i);
}
cout << endl;

Concatenation #

string objects can be concatenated using the + operator.

string first = "John";
string last = "Doe";
string name = first + " " + last;

This also sometimes works with non-string types, but not always as the compiler might not know how to use the + operator.

int videoWidth = 1920;
int videoHeight = 1080;
string resolution = videoWidth + "x" + videoHeight;  // OK?

float videoWidthf = 1920;
float videoHeightf = 1080;
string resolutionf = videoWidthf + "x" + videoHeightf;  // ERROR!

OF has ofToString() helper functions, which can be used to convert other variable types into string.

int videoWidth = 1920;
int videoHeight = 1080;
string resolution = ofToString(videoWidth) + "x" + ofToString(videoHeight);

float videoWidthf = 1920;
float videoHeightf = 1080;
string resolutionf = ofToString(videoWidthf, 1) + "x" + ofToString(videoHeightf, 1);