Data types in C++ Programming

Data types in C++ are meant to identify and inform compiler the type of data, memory and associated operations of handling it. Variable in C/C++ both use data-type during declaration to restrict the type of data to be stored. Every data type requires different amount of memory allotted by compiler.

There are three types of data types:

1. Primary(Built-in) Data Types
2. User Defined Data Types
3. Derived Data Types

Primary Data Types

Primary data types are built-in or predefined data types that can be used directly by the user to declare variables. There are six different data types in C++ and most this are same as of C language except Boolean and wide character.

This article contains very little details of this type if you need more you can study this article.

• Character: Keyword ‘char’ used to store character data type like a-z, A-Z and special symbols (@, !, %). This Characters type requires 1 byte of memory and ranges from -128 to 127 or 0 to 255.
• Integer: As the name suggests it holds only integer values requires 4 bytes of memory space and value ranging from -2147483648 to 2147483647. Keyword ‘int’ used for integer data types.
• Floating Point: Keyword ‘float’ used to stores real numbers known as Floating Point. Float type used to store single precision floating point values or decimal values. It requires 4 byte of memory space.
• void: Void data type used to represents a valueless entity. Void data type mostly used for function which does not returns a value. Please see this article for more details about above four data type.
• Boolean: Boolean data type used for storing logical values in variables. A Boolean type can store either true or false OR 0 or 1. Keyword ‘bool’ used for this type of variable.
• Wide Character: Wide character is similar to char data type but the difference is the size of wide character is greater than the normal 1 byte datatype. Generally Wide char is 2 or 4 bytes long and keyword ‘wchar_t’ used.

//program to demonstrate use of wchar_t
#include <iostream>
using namespace std;

int main()
{
    wchar_t w  = 'a';
    wcout << "Wide character value: " << w << endl ;
// w prefixed in operations like printing (wcout) while operating on wide-char type
    cout << "Size of the wide char is: " << sizeof(w);
    return 0;
}

Output:

Wide character value: a
Size of the wide char is: 2

Datatype               size 	Range limit             format specifier
char	                 1 	   −128 to 127                         %c
signed char	             1 	   −128 to 127                         %c
unsigned char	         1 	   0 to 255                            %c
short int                2 	  -32,768 to 32,767 	               %hd
unsigned short int 	     2 	   0 to 65,535 	                       %hu
unsigned int 	         4 	   0 to 4,294,967,295 	               %u
int 	                 4 	   -2,147,483,648 to 2,147,483,647 	   %d
long int 	             4     -2,147,483,648 to 2,147,483,647 	   %ld
unsigned long int        4 	   0 to 4,294,967,295 	               %lu
long long int 	         8 	   -(2^63) to (2^63)-1 	               %lld
unsigned long long int   8 	   0 to 18,446,744,073,709,551,615 	   %llu
float 	                 4 	   1.2E-38 to 3.4E+38	               %f
double 	                 8 	   2.3E-308 to 1.7E+308	               %lf
long double 	         12    3.4E-4932 to 1.1E+4932	           %Lf

We can display the size of all the data types by using the sizeof() function and passing the keyword of the datatype as argument .

// C++ program to show size of data types 
#include<iostream> 
using namespace std; 
  
int main()
{
    cout << "Size of char : " << sizeof(char)<<endl;

    cout << "Size of int : " << sizeof(int)<<endl;

    cout << "Size of float : " << sizeof(float)<<endl;

    cout << "Size of double : " << sizeof(double)<<endl;

    return 0;
}

Output:

Size of char : 1
Size of int : 4
Size of float : 4
Size of double : 8

User-Defined Data Types:

User defined data type are defined by user itself. Like, defining a class, structure, in C++.

These types include:

• Structure
• Union
• Enumeration
• Typedef
• Class

Brief description of these one by one:

struct name{
  	char name[10];  //data member
  	int R_no;
  	float percent;
};

union name_of_union{
  	int X;
  	float Y;
  	long double Z;  // union size is equal to long double i.e. 12
};

enum day {monday, tuesday, wednesday, thursday, friday, saturday};

enum State {Working = 1, Failed = 0}; // explicit assignment

typedef int INTEGER;

int main()
{
INTEGER num1 = 1, num2 = 2;
printf("%d %d",num1,num2);

return 0;
}

Output:

1 2

class nameofclass{
access specifier:              // public, private or protected
data members;              // data variable
member functions       // this function used to access data members and 
                    //may or may not contain definition inside class
}

// Class example program
#include<iostream>
using namespace std;

class add{
    int a,b;
public:
    int getab(int x,int y){
        a = x;
        b = y;
        return a+b;

    }
};


int main()
{
add obj;
cout << "Add : " << obj.getab(5,4)<<endl;

    return 0;
}

Output:

Add : 9

Derived Data Type

Derived data type is a data type in C++ which are built from basic data types like Float,int,double,etc.

int function()      // function with int return type

int main()
{
}

#include<iostream> 
using namespace std; 
  
int main() 
{ 
  int a = 1; 
  
  // reference to a. 
  int& b = a; 
  
  // a is changed to 2 
  b = 2; 
  cout << "a = " << a << endl ; 
  
  // a is changed to 3 
  a = 3; 
  cout << "b = " << b << endl ; 
  
  return 0; 
}

Output:

a = 2
b = 3

int main(){
int i=10;
int *j;        // integer pointer
j=&i;      // i address assigned to j

printf("%d %p",i,j);  // %p is a format specifier for pointer
// OUTPUT will be different for you
return 0;
}

Output:

10 0060FF08

int arr1[10] = {1,2,3,4,5,6,7,8,9,10};