Please refer this Day 2: C++ language - output before you proceed .
Topics to be covered
- Variables or identifiers
- Datatype
- Declaration of variables
- 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.
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.
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 .
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.
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 .
Boolean - Stores true or false values.
bool she_girl = True ;
here boolan is the datatype and she_girl is the variable .
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 ;
It is okay to declare and initialise the variable in same line .
int myVariable = 10 ;
float myotherVariable = 34.10 ;
Or
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 :
myvariableor_myage.Names are case sensitive or C++ language is case sensitive ie,
myvariableandMYVARIABLEorMyvariableare 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).
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