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:

  • Structure: structure creates a data type that used to group items of different relative data types into a single type. Keyword “struct” used followed by structure name to define the structure
  • struct name{
      	char name[10];  //data member
      	int R_no;
      	float percent;
    };
  • Union: Union is similar to structure except that all members share the same memory location and the size of memory it gets is equal to the largest data type the union contain.
  • union name_of_union{
      	int X;
      	float Y;
      	long double Z;  // union size is equal to long double i.e. 12
    };
  • Enumeration: Enumeration mainly used to assign names to integral parts. We can also explicitly assign the enumeration constants. This names make a program easy to read and debug.
  • enum day {monday, tuesday, wednesday, thursday, friday, saturday};
    
    enum State {Working = 1, Failed = 0}; // explicit assignment
  • Typedef: typedef is used to explicitly define new data type names or alias name of existing data type.
  • typedef int INTEGER;
    
    int main()
    {
    INTEGER num1 = 1, num2 = 2;
    printf("%d %d",num1,num2);
    
    return 0;
    }

    Output:

    1 2
  • Class: Class is a user defined data type with its own data members and member functions accessed and used by creating an instance or object of that class. A class is a blueprint for an object.
  • 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.

  • Function: Function in C++ is a derived data type depending upon its return type. for example, if a function is returning int value than the Function returning int type.
  • int function()      // function with int return type
    
    int main()
    {
    }
  • Reference: Reference is an alternative name for already existing variable declared by putting ‘&’ in the declaration. Reference is safer than pointers as it cannot be void and must be declared n defined at same time.
  • #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
  • Pointers: Pointers contains the address of another variable in the memory.
  • 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
  • Arrays: An array is a collection of data of homogeneous data, stored in contiguous memory locations
  • int arr1[10] = {1,2,3,4,5,6,7,8,9,10};
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