Identifier refers to name given to different entities such as constants, variables, structures, functions, etc.
mobile_number are identifier
. int and
double are data type.
Rules for naming Identifier
- We cannot use keywords as identifier.
- The first letter of an identifier should be either a letter or an underscore. An identifier can start with the alphabet, and underscore only. It can’t start with a digit.
- No whitespace, commaare allowed within the identifier.
- Identifiers are case sensitive.
- There is no rule on how long an identifier can be. However, you may run into problems in some compilers if the identifier is longer than 31 characters.
** There is a total of 63 alphanumerical characters that represent the identifiers.
|Capital letter (Uppercase) in the English alphabet||26|
|Small letter (Lowercase) in the English alphabet||26|
Keyword vs Identifier
|Keyword is a pre-defined word.||Identifier is a user-defined word|
|It is a combination of alphabetical characters.||It is a combination of alphanumeric characters.|
|It can only be written in lowercase||It can be written in lowercase and uppercase letters.|