C++ identifiers are names that identify program elements such as variables using alphabets, numbers, and underscore.
Here is the list of characters for:
- Alphabets: a … z, A … Z
- Numbers: 0 … 9
- Underscore: _
Any other character from your keyboard that does not fall under the above category is called a special character. The uppercase and lowercase are distinct characters. They have different numeric values according to ASCII standard.
There is no limit for the number of characters used as identifiers, but some compiler put limitation by recognizing first “n” characters as identifier name. You should read the compiler documentation to get the information.
Rules for Variable Names
The C++ identifiers are used for variable names. We must learn the rules to give valid names to variables. The names must contain allowed characters.
My_var Table S R
The above are some valid names.
5chair speeed$boat three dimension
The above three variable names are invalid because:
- variable names cannot begin with a number
- special characters are not allowed
- whitespace is not allowed for variable names.
Keywords are special identifiers because they are reserved by the compiler. You cannot use them as variable names and they are case sensitive.
Here is a list of C++ keywords.
Note that sometimes one or more keywords are used together.