Variable in C/C++

Definition:

It is a data name which is used to store data and may change during execution. A variable is  used to create and locate the data at  a particular location in computer's memory. Variable is data item whose value can be changed during the exam execution.

syntax:


  data_type variable_name;

Rules of variable name:

• Variable must start with a letter.
• Variable name can contain letters, numbers and the underscore.
• Keywords are not allowed to use as a variable name.
• Variable name can not have space in between.
• Variable name can not have special character.

Scope of variable:

A variable can be either of global or local scope. A global variable is a variable declared in the main body of the source code, outside all the functions. While a local variable is one declared within the body of a function or a block. 

Declaration of variable:

C++ allows the declaration of a variable can be declared right at the place of its first use. This make the program much easier to write.

Example program:

int main()
{
int num1, num2, result;                               //variable declaration
cout<<"Enter first number:";
cin>>num1;
cout<<"Enter second number:";
cin>>num2;
result=num1+num2;
cout<<"\n Addition is:"<<result;
return 0;
}

OUTPUT:

Enter first number:2 
Enter second number:3
Addition is:5