C++ Identifiers and Keywords with Examples

In this article, you will learn about "identifiers" and "keywords," the two most important topics when discussing C++ programming. So, without further ado, let us start with the identifiers.

What are identifiers?

Identifiers are the basic building blocks of a program. Identifiers are used as a general name given to different parts of the program, namely variables, objects, classes, functions, arrays, etc.

Since C++ is a case-sensitive language, therefore, "codescracker,"  "Codescracker,"  "CodesCracker,"  and "CODESCRACKER" are all four different identifiers.

Before moving further, let's first understand the rules for creating an identifier in C++.

Rules to create or name an identifier in C++

To create an identifier in the C++ language, you need to follow the following rules:

  • An identifier must begin with a letter from A to Z, a-z, or _ (an underscore character).
  • Then we can add letters (A-Z, a-z), digits (0-9), and underscores to its name.
  • Reserved words (keywords) are not allowed to be used as identifiers.

Following is a list of some valid identifiers. This list is included for your convenience because examples help to make the topic more understandable.

  • codes_cracker
  • Myvar
  • _myvar
  • _my34var_
  • sum_of_two_numbers

Tip: You may either use underscore in variable names to separate parts of the name, such as last_name, first_name, and main_balance, or you may go for "capital style" notation, such as lastName, firstName, and mainBalance, i.e., capitalizing the first letter of the next word.

C++ Identifiers Example

The following C++ program is an example program of C++ identifiers that will give you an idea of how identifiers are used in C++ programming:

#include<iostream>
using namespace std;
int main()
{
   char ch;
   char name[20];
   int num;

   cout<<"Enter a character: ";
   cin>>ch;
   cout<<"You entered: "<<ch<<endl;

   cout<<"\nEnter your name: ";
   cin>>name;
   cout<<"Your name is: "<<name<<endl;

   cout<<"\nEnter a number: ";
   cin>>num;
   cout<<"You entered: "<<num<<endl;

   return 0;
}

When the above C++ program is compiled and executed, it will produce the following output:

c++ identifiers

Now supply the input, say "c," as a character, and hit the "ENTER" key. Then supply another input, say "codescracker," as a name, and again hit the "ENTER" key. The following snapshot shows the sample run of the above C++ example program.

c++ identifiers example

The cout<<endl; and cout<<"\n"; both insert a line break on the output console. You can refer to "endl" as "end-line."

Keywords in C++

To a language compiler, certain words have a heightened significance, and these are known as keywords. Because these are reserved words that are used for specific purposes, you are not allowed to use them as regular identifier names.

I previously stated that reserved words or keywords may not be used as identifiers. As a result, it is critical to remember the list of keywords so that you do not accidentally use them as identifiers. As C++ keywords, keep the following list in mind:

  • alignas
  • decltype
  • namespace
  • struct
  • alignof
  • default
  • new
  • switch
  • and
  • delete
  • noexcept
  • template
  • and_eq
  • do
  • not
  • this
  • asm
  • double
  • not_eq
  • thread_local
  • auto
  • dynamic_cast
  • nullptr
  • throw
  • bitand
  • else
  • operator
  • true
  • bitor
  • enum
  • or
  • try
  • bool
  • explicit
  • or_eq
  • typedef
  • break
  • export
  • private
  • typeid
  • case
  • extern
  • protected
  • typename
  • catch
  • false
  • public
  • union
  • char
  • float
  • register
  • unsigned
  • char16_t
  • for
  • reinterpret_cast
  • using
  • char32_t
  • friend
  • return
  • virtual
  • class
  • goto
  • short
  • void
  • compl
  • if
  • signed
  • volatile
  • const
  • inline
  • sizeof
  • wchar_t
  • constexpr
  • int
  • static
  • while
  • const_cast
  • long
  • static_assert
  • xor
  • continue
  • mutable
  • static_cast
  • xor_eq

More Examples

C++ Quiz


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