Data Types And Variables In C++

Variable:

Variable means whose value can be changed.

Variable contains value which is stored in memory and holds some space.

Every Variable is assigned a datatype which shows size(2 byte,4 byte etc.) and type of data type(int,float etc)

2 steps to use variables

·        Variable Declaration

·        Variable Initialization

Variable Declaration:

Syntax: 

Datatype variablename;

Eg 1:

int x;

Where int is the data type and x is the variable name.

Eg 2:
float y;    
char ch;   
char name[20];

    Where float, char,string are the  data type, y,ch and name are the variables.

Variable Initialization:

Syntax:

Datatype variablename=value;

Eg 1:

int x=89;

Where int is the data type, x is the variable name and 89 is the value which assigned to x.

Eg 2:

float y=78.90;    

    char ch=’A’;    
   char name[20]=”LearningPoint92”;

Rules for defining variables

It can have alphabets, digits and underscore.

A variable name should start with alphabet and underscore only. It can't start with digit.

No white space is allowed within variable name.

A variable name can not be any reserved word or keyword e.g. double, float etc.

Valid variable declaration:
int x;    

     int _xy;    

      int x45;    

Invalid variable declaration:
 int 7;   
 int x y;  
 int float;  

Data Types:

Data types are used to store different values in the variable. There are four types of data types in c++.

•  Basic (int ,float,char,double etc)  
• Derived(array,pointer etc) 
• Enumeration(enum)  
• User Defined(Structure)

char

Data types	Size	Range
char	1 byte	-128 to 127
signed char	1 byte	-128 to 127
unsigned char	1 byte	0 to 127

short

Data types	Size	Range
short	2 byte	-32,768 to 32,767
signed short	2 byte	-32,768 to 32,767
unsigned short	2 byte	0 to 32,767

int

Data types	Size	Range
int	2 byte	-32,768 to 32,767
Signed int	2 byte	-32,768 to 32,767
Unsigned int	2 byte	0 to 32,767

short int

Data types	Size	Range
Short int	2 byte	-32,768 to 32,767
Signed short int	2 byte	-32,768 to 32,767
Unsigned short int	2 byte	0 to 32,767

long int

Data types	Size
long int	4 byte
Signed long int	4 byte
Unsigned long int	4 byte

float and double

Data types	Size
float	4 byte
double	8 byte
long double	10 byte