Variables in CPP (C Plus Plus)
Variables in CPP (C Plus Plus)
A variable is used to store the values. The name of a variable is called an identifier. You can give a variable any name of your choice, as long as it is a valid identifier name and the Variable name must be descriptive.
Every variable must have the name, type, size, value, and address.
Name — a variable name like the price
Type — variable type like integer, string
Size — determined by the type
Value — the data stored in the variable’s memory location
Address — the starting location in memory where the value is stored.
Syntax of variable declaration
data_type variable_name; (Example: int price)
data_type variable_name1, variable_name2, variable_name3; (Example: int a, b, c)
Examples of variable declaration
int marks;
char ch;
float unit;
double meter_to_cm;
int marks;
int chemistry_marks, computer_marks;
Variable Initialization
Variables can be initialized with values.
Initialization of integers
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int marks=600; |
Declaration and initialization on a different line
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int number; number=60; |
Initialization of Characters
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char name; name='ali'; |
RULES FOR NAMING VARIABLES
Rule 1:
All variable names must start with an alphabet or an Underscore ( _ ).
Example:
char _price;
float cost;
Rule 2:
After the first initial letter, variable names can also contain numbers. A variable name can’t start with a number.
Example:
“a1” variable name is legal but “1a” is not a legal name.
Rule 3:
Spaces or special characters are not allowed.
Example:
float product price //wrong variable name because it has space in the variable name.
float product_price //Correct variable name because it has no space in the variable name.
Rule 4:
Uppercase characters are distinct from lowercase characters.
Example:
float PRICE and float price both are different.
Rule 5:
You cannot use a C++ keyword (a reserved word) as a variable name.
Example:
float char; // “char” is a wrong variable name. char is a keyword and it is not allowed in the variable name.
SCOPE OF VARIABLE IN C++
Local Variable
Variables that are declared inside a function or block are local variables. They can be used only by statements that are inside that function or block of code.
Example of Local Variable
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#include <iostream> //header file using namespace std; int main () { float price=4; //Local variable declaration: cout << price; //output } |
Global Variable
Global variables are variables that are often declared outside the main() function. The variable scope is the full file where the variable is defined.
The global variable can be defined as below.
Example of Global Variable
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#include <iostream> //header file using namespace std; float price=4; //price is a Global variable int main () { cout << price; //output } |