C++ Variables, Constants and literals

In this blog post, we will learn about variables, constants, and literals in C++ with the help of examples.

C++ Variables:

A variable is a storage location that contains some value known or unknown. A symbolic name (identifier) is associated with a variable and usually, we used this name to refer to the stored value.

Let’s see an example of how we can create a variable in programming.

//A general syntax for variable declaration

data_type var_name;

//integer variable

int  weight = 27;

The above statement tells the program that it is storing an integer and that the name weight represents the integer’s value. Here weight is representing 27 (integer).

When the above statement will execute a chunk of memory will allocate to store the integer value. Using the ‘weight’ we can access the memory to read the store value (27). If you want you can also change the store value by using the below statement.

//changing weight value


weight = 6;

The variable name does not give you information that where in-memory value is stored, but using the & operator we can retrieve the address of the variable. In our next post, we will see it in detail.

Naming Rule of the variable in C++:

A variable name can be composed of letters, digits, or underscore. C++ is a case-sensitive language so upper and lower case are totally different from each other. for example, data and DATA both are two different variables.

1. A variable name should not contain space.

int data Len; (wrong)

int dataLen; (correct)

2. A variable name can only have alphabets, numbers, and the underscore ( _ ).

3. A variable name cannot start with a digit but you can use it between or end of the identifier.

int 2length; (wrong)

int le2ngth; (correct)

4. You cannot use a special character in identifiers except the underscore.

int len@gth; (wrong)

int le#ngth ; (wrong)

int len_gth; (correct)

int _length; (correct)

5. A variable name cannot be a keyword.

int if; (wrong)

int while; (wrong)

Note: We always try to give meaningful names to variables and should follow single notation in projects, like camel case or Hungarian notation both are very popular.

C++ Constants:

The const keyword is a qualifier, it changes the behavior of the variable and makes it a read-only type. When we want to make an object read-only type, then we have to declare it as const.

const int data = 0;

data = 10 // Compiler Error because data is a constant.

In another separate article, we will read the const qualifier in detail.