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Variables
Variables are memory locations used to store values. When a variable is created, some space is
allocated in the memory for it. This memory space is referred by the name that we give to the
variable. The name we give to a variable is called an identifier.
Naming Conventions for Variables
Following are the naming conventions used to declare a variable in C++:
A variable name must start with a letter (a–z, A–Z) or an underscore ( _ ).
A variable name cannot start with a digit.
Keywords cannot be used as variable names.
A variable can only contain alpha-numeric characters and underscore (A–Z both capital as
well as small) and (0–9) numbers.
No special symbols like ! , @ , #, $, %, etc. can be used in variable name.
Variable names are case sensitive.
Variable names cannot contain blank space.
Examples of some valid variable names are:
Valid Variable Name Reason
Gaurav123 Starts with a letter
_usha93 Starts with an underscore symbol
Examples of some invalid variables are:
Invalid Variable Name Reason
1_Name Cannot start with a digit
@Address Cannot starts with a special symbol excluding
underscore (_)
int Keyword cannot be used as variable name
User Name White space is not allowed in variable names
Declaring a Variable
C++ is a strongly-typed language, which means you need to declare a variable before using it.
You also need to specify the data type of the variable, so that the compiler understands how the
variable is interpreted. When a variable is declared, some space is reserved for it in the memory
of the computer. Syntax to declare a variable in C++ is as follows:
<type> <variable_name>;
Where, type is the data type that specifies the type of value a variable can store and
variable_name is the name of the variable which is used to access the variable in the program.
Getting Started with C++ 15

