方便查找之用
关键字是预先保留的标识符，每个关键字都有特殊的含义。我们不能在程序中使用与关键字同名的标识符。以下是C＋＋所保留的关键字 （66个）
| asm | auto | bad_cast | bad_typeid |
| bool | break | case | catch |
| char | class | const | const_cast |
| continue | default | delete | do |
| double | dynamic_cast | else | enum |
| except | explicit | extern | false |
| finally | float | for | friend |
| goto | if | inline | int |
| long | mutable | namespace | new |
| operator | private | protected | public |
| register | reinterpret_cast | return | short |
| signed | sizeof | static | static_cast |
| struct | switch | template | this |
| throw | true | try | type_info |
| typedef | typeid | typename | union |
| unsigned | using | virtual | void |
| volatile | while |