DEV Community

Mehfila A Parkkulthil
Mehfila A Parkkulthil

Posted on

Day 3: C++ language | Variables | Datatypes | Part-1

#vscode #cpp #dsa #coding

Please refer this Day 2: C++ language - output before you proceed .

Topics to be covered

  1. Variables or identifiers
  2. Datatype
  3. Declaration of variables
  4. General rules of variables

Variables

Variables or identifiers are containers for storing data values or a variable is a named storage location in memory that can hold a value. The value of a variable can be changed during the execution of a program.

Datatype

Data types specify the kind of data a variable can hold.The most common are integer(int) , float or double , character(char), string , boolean(bool) etc .

Integer - Stores whole numbers without decimal points.

Will be explained in detail later.
Imagine if 

int age = 13;
here int is the datatype and age is the variable and 13 is value.
Enter fullscreen mode Exit fullscreen mode

Float - Stores numbers with fractional parts, i.e., numbers with decimals.

float price = 22.34;
here float is the datatype and price is the variable and 22.34is value.
Enter fullscreen mode Exit fullscreen mode

Double -Similar to float but with double the precision. It can store larger and more precise numbers.

double distance = 12345.6789;
here double is the datatype and distance is the variable .
Enter fullscreen mode Exit fullscreen mode

Character-Stores a single character, usually within single quotes.

char initial = 'A';
here character is the datatype and initial is the variable 
and 'A' is the value.
Enter fullscreen mode Exit fullscreen mode

String- Stores text (sequences of characters).Strings should be stored in double quoted.

string greet = "Hello, World!";
here string is the datatype and greet is the variable .
Enter fullscreen mode Exit fullscreen mode

Boolean - Stores true or false values.

bool she_girl = True ;
here boolan is the datatype and she_girl is the variable .
Enter fullscreen mode Exit fullscreen mode

Variable declaration

Decalaration and initialisation of variables

Variable declaration is the way you tell a programming language to set aside a part of memory to store data. You do this by specifying the variable name and sometimes its type.

Variable initialization is the process of assigning an initial value to a variable at the time of its declaration

In C++, you have to specify the type of the variable when you declare it.

Example :

To initialise the variable should be declared.

Emaple1:

// Declaration
int myVariable; 

// Initialization
myVariable = 10; 



Example2:

// Declaration
float myotherVariable; 

// Initialization
myotherVariable = 34.10 ;
Enter fullscreen mode Exit fullscreen mode

It is okay to declare and initialise the variable in same line .

int myVariable = 10 ;
float myotherVariable = 34.10 ;
Enter fullscreen mode Exit fullscreen mode

initialisation and declaration

Or

Initialisation and declaration

Rules of Variables

  • All c++ variables must have unique names . These unique names are called identifiers.

  • Names can contain letters , digits and underscores.

  • Names must begin with letter or an underscore . Example : myvariable or _myage .

  • Names are case sensitive or C++ language is case sensitive ie, myvariable and MYVARIABLE or Myvariable are not same.

  • Names cannot contain white spaces or any special characters like ! , # , % etc.

  • Reserved names cannot be variables .(Reserved or keywords will be explained later).

Previous Blog

Top comments (0)