C++ Identifiers

  C++ Identifiers

C++ identifiers in a program are used to refer to the name of the variables, functions, arrays, or other user-defined data types created by the programmer. They are the basic requirement of any language. Every language has its own rules for naming the identifiers.

In short, we can say that the C++ identifiers represent the essential elements in a program which are given below:

1.Constants

2.Variables

3.Functions

4.Labels

5.Defined data types

Some naming rules are common in both C and C++. They are as follows:

Only alphabetic characters, digits, and underscores are allowed.

The identifier name cannot start with a digit, i.e., the first letter should be alphabetical. After the first letter, we can use letters, digits, or underscores.

In C++, uppercase and lowercase letters are distinct. Therefore, we can say that C++ identifiers are case-sensitive.

A declared keyword cannot be used as a variable name.

For example, suppose we have two identifiers, named as 'FirstName', and 'Firstname'. Both the identifiers will be different as the letter 'N' in the first case in uppercase while lowercase in second. Therefore, it proves that identifiers are case-sensitive.

 Valid Identifiers

The following are the examples of valid identifiers are:

Result  

Test2 

_sum

 power  

Invalid Identifiers

The following are the examples of invalid identifiers:

Sum-1   // containing special character '-'.  

2data    // the first letter is a digit.  

break    // use of a keyword.    

 Let's look at a simple example to understand the concept of identifiers.

include <iostream>

  using namespace std; 

 int main() 

 {  

int a;  

int A;  

cout<<"Enter the values of 'a' and 'A'";  

cin>>a;  

cin>>A;  

cout<<"\nThe values that you have entered are : "<<a<<" , "<<A;   

return 0; 

 }  

output :