C++ Keywords
C++ keywords are the reserved words which are pre-defined in C++ programming language. We cannot use keywords as an identifier. Each keyword has a pre-defined meaning for C++ compiler.
- Trying to use a keyword as an identifier will generate a compilation error.
- All keywords are in lower case letters.
| asm | else | new | this |
| auto | enum | operator | throw |
| bool | explicit | private | true |
| break | export | protected | try |
| case | extern | public | typedef |
| catch | false | register | typeid |
| char | floar | reinterpret_cast | typename |
| class | for | return | union |
| const | friend | short | unsigned |
| const_cast | goto | signed | using |
| continue | if | sizeof | virtual |
| default | inline | static | void |
| delete | int | static_cast | volatile |
| do | long | struct | wchar_t |
| double | mutable | switch | while |
| dynamic_cast | namespace | template |
C++ Identifiers
In C++ programming language, the name of variables, functions, labels, classes and user-defined entities are called Identifiers. Each element of a C++ program are given an identifier. A C++ identifier can be of any length, there is no limit on the length of the identifiers in C++.
For Example:int Interest; int getSimpleInterest(int amount);
Interest is an identifier for a variable of integer data type and getSimpleInterest is an identifier for a function. C++ identifiers are case sensitive, which means 'value' and 'Value' will be treated as two different identifiers.
- An identifier cannot be same as a C keyword.
- The first character of an identifier must be either an alphabet or underscore.
- An identifier can be composed of alphabets, digits, and underscore only.
- Identifier name is case sensitive. "Home" and "home" is recognised as two separate identifiers.
- Any special characters other than alphabets, digits, and underscore (such as :, . ,blank space, / are not allowed).
Here are few examples of valid and invalid Identifiers.
| Valid Identifiers | Invalid Identifiers |
|---|---|
| hello | 1hello |
| Hello | Hel/lo |
| _hello | hel lo |
| hello_world | hello,,,world |