Identifiers in C++

by - February 15, 2019

Identifiers in C++

Identifier

C++ identifiers are names used to identify variable, function, class or any other user-defined items. For Example Variable name, Function name, Class name, structure name.

An identifier starts with a letter either capitals (A to Z) or small (a to z) or an underscore _ that does not begin with a digit. C++ does not allow us to use punctuation characters such as -, @, $ and % within identifiers. C++ is a case sensitive programming language. Thus, Demo and demo are two different identifiers.

Valid Identifiers: Foo, _demo, abc, move_name, a_123, myname50, _temp, a23b9, retVal

Invalid Identifiers: 1Demo, a-123, demo@dss, Amount$100, a%b

Rules for naming an identifier

  1. Identifier name must begin with a letter, either capital (A to Z) or small (a to z).
  2. Identifier name does not begin with a digit (0-9).
  3. It must not contain any space or tab.
  4. Keywords cannot be used as an identifier.
  5. Special Symbols are not allowed in identifier names.
  6. Length of an identifier is at most 32 characters.
  7. Identifiers are case sensitive.

Let’s discuss some examples

Name
Use
Explanation
1sal
No
Because identifier does not begin with a digit.
first name
No
Because there should be no space or tab.
age@
No
Because it does not contain special letters.
While
Yes
Because While is not a keyword. (W is capital and small w is for keyword).
_rent
Yes
Begins with an underscore.
for
No
Because it is a keyword.
last_name
Yes
Because it contains letters and underscore and there is no space between them.


Conventions for naming identifiers

Following conventions is a good practice because it increases the readability of code. It makes the code easier to understand and thus help many people understand the code.

  • Use only letters either capital or small.
  • Use camelCase style for naming an identifier.
  • Choose a name which genuinely shows its work.

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