Basic Data Type and Variable in C++

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Variable:-

In the C++ programming language, you need to use various variables to store various information. Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in memory.

Data type:-

A data type determines the type and the operations that can be performed on the program, In a C++ to declare a type of variable use a various data types like character, wide character, integer, floating point, double floating point, boolean etc. Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the reserved memory.

So, we can say Data types define the type of data a variable can hold.

Data Type in C++:-

1.        Primary(Built-in) Data Types:

                                                     These data types are predefined data types and can be used directly by the user to declare variables. example: int, char , float, bool etc. Primitive data types available in C++ are:

Type Boolean Character Integer Floating point Double floating point Valueless Wide character

Keywords Bool Char int float double void wchar_t

§ 

Integer

: Int is keyword of an integer, it is use to declare a integer in a C++ with the help of it’s keyword. Integers typically requires 4 bytes of memory space and ranges from -2147483648 to 2147483647.

How to write a integer in C++ it’s given blew:-

int a = 10;

§  Character: 

                        To declare a character in C++ use Char. Char is a keyword of character. Character data type is used for storing characters. Characters typically requires 1 byte of memory space and ranges from -128 to 127 or 0 to 255.

How to write a character in C++ it’s given blew:-

char ch = 'I';

§  Boolean: 

                Bool is keyword of Boolean. Boolean data type is used for storing boolean or logical values. A boolean variable can store either true or false.

How to write a boolean in C++ it’s given blew:-

bool b = true;

§  Floating Point:

                            Floating Point data type is used for storing single precision floating point values or decimal values. Float variables typically requires 4 byte of memory space.

How to write a float in C++ it’s given blew:-

float num = 12.789;

§  Double Floating Point:

                                        Double Floating Point data type is used for storing double precision floating point values or decimal values. Keyword used for double floating point data type is double. Double variables typically requires 8 byte of memory space.

 

               How to write a double in C++ it’s given blew:-

double num = 23.987;

§  void: Void means without any value. void datatype represents a valueless entity. Void data type is used for those function which does not returns a value.

§  Wide character:-   Wide character data type is also a character data type but this data type has size greater than the normal 8-bit datatype. Represented by wchar_t. It is generally 2 or 4 bytes long.

Datatype Modifiers: As the name implies, datatype modifiers are used with the built-in data types to modify the length of data that a particular data type can hold. Data type modifiers available in C++ are:

§  Signed

§  Unsigned

§  Short

§  Long

Below table summarizes the modified size and range of built-in datatypes when combined with the type modifiers:-

DATA TYPE	SIZE(IN BYTES)	RANGE
Short int	2	-32,768 to 32,767
Unsigned int	2	0 to 65,535
Unsigned int	4	0 to 4,294,967,295
Int	4	-2,147,483,648 to 2,147,483,647
Long int	4	-2,147,483,648 to 2,147,483,647
Unsigned long int	4	0 to 4,294,967,295
Long long int	8	-(2^63) to (2^63)-1
Unsigned long long int	8	0 to 18,446,744,073,709,551,615
Signed char	1	-128 to 127
Unsigned char	1	0 to 255
Float	4
Double	8
Long double	12
Wchar_t	2 or 4	1 wide character

We can display the size of all the data types by using the size_of() function and passing the keyword of the datatype as argument to this function as shown below:

// C++ program to sizes of data types #include<iostream> using namespace std; void main() {     cout << "Size of char : " << sizeof(char) << " byte" << endl;     cout << "Size of int : " << sizeof(int) << " bytes" << endl;     cout << "Size of short int : " << sizeof(short int) << " bytes" << endl;     cout << "Size of long int : " << sizeof(long int) << " bytes" << endl;     cout << "Size of signed long int : " << sizeof(signed long int) << " bytes" << endl;     cout << "Size of unsigned long int : " << sizeof(unsigned long int) << " bytes" << endl;     cout << "Size of float : " << sizeof(float) << " bytes" <<endl;     cout << "Size of double : " << sizeof(double) << " bytes" << endl;     cout << "Size of wchar_t : " << sizeof(wchar_t) << " bytes" <<endl;           getch (); }

This example uses endl, which inserts a new-line character after every line and << operator is being used to pass multiple values out to the screen. We are also using sizeof() operator to get size of various data types.

When the above code is compiled and executed, it produces the following result which can vary from machine to machine −

Output:- Size of char : 1 byte Size of int : 4 bytes Size of short int : 2 bytes Size of long int : 8 bytes Size of signed long int : 8 bytes Size of unsigned long int : 8 bytes Size of float : 4 bytes Size of double : 8 bytes Size of wchar_t : 4 bytes

2.      User Defined Data Types:

       I.            Structure
II.            Union
III.          Class
IV.           Enumeration

3.      Derived Data Types:

       I.            Array
II.            Function
III.          Pointer
IV.           Reference

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