Undeclared identifier:XXX
未识别错误，是因拼写错误或找不到定义文件。
下面列举一些类型和函数用到的单元。
| _Stream | ADODB_TLB |
| akTop, akLeft, akRight, akBottom | Controls |
| Application (the variable not a type) | Forms |
| Beep | SysUtils or Windows (different functions) |
| CGID_EXPLORER | ShlObj |
| CN_BASE | Controls |
| CoInitialize | ActiveX |
| CopyFile | Windows |
| CoUnInitialize | ActiveX |
| CreateComObject | ComObj |
| CreateOleObject | ComObj |
| Date | SysUtils |
| DeleteFile | SysUtils or Windows (different versions) |
| DispatchInvokeError | ComObj |
| DWORD | Windows |
| EDatabaseError | DB |
| EncodeDateTime | DateUtils |
| EnumWindows | Windows |
| EOleError | ComObj |
| EOleException | ComObj |
| EOleSysError | ComObj |
| Exception | SysUtils |
| ExtractFileName | SysUtils |
| FileExists | SysUtils |
| FileOpen | SysUtils |
| FILETIME | Windows |
| FindFirst | SysUtils |
| FindFirstFile | Windows |
| FindWindow | Windows |
| FlushFileBuffers | Windows |
| fmOpenRead | SysUtils |
| fmShareDenyWrite | SysUtils |
| Format | SysUtils |
| FormatDateTime | SysUtils |
| FreeAndNil | SysUtils |
| fsBold | Graphics |
| ftWideString | DB |
| ftString | DB |
| GetCurrentProcessId | Windows |
| GetEnvironmentVariable | SysUtils or Windows (different versions) |
| GetFileAttributes | Windows |
| GetFileVersionInfoSize | Windows |
| GetWindowLong | Windows |
| GetStdHandle | Windows |
| HDC | Windows |
| HFont | Windows |
| HINTERNET | WinInet |
| HKEY_CURRENT_USER | Windows |
| IHTMLDocument2 | MSHTML or MSHTML_TLB |
| IHTMLElement | MSHTML or MSHTML_TLB |
| IHTMLEventObj | MSHTML or MSHTML_TLB |
| IID_IWebBrowser2 | SHDocVw or SHDocVw_TLB |
| IMessage | CDO_TLB |
| InternetClosehandle | WinInet |
| InternetOpenUrl | WinInet |
| InternetReadFile | WinInet |
| IntToHex | SysUtils |
| IntToStr | SysUtils |
| IOleCommandTarget | ActiveX |
| IOleContainer | ActiveX |
| IPersistStreamInit | ActiveX |
| IsSameDay | DateUtils |
| IStream | ActiveX |
| IWebBrowser2 | SHDocVw or SHDocVw_TLB |
| LockWindowUpdate | Windows |
| Log10 | Math |
| LowerCase | SysUtils |
| LPSTR | Windows |
| MAX_PATH | Windows |
| MessageBox | Windows |
| MessageDlg | Dialogs |
| MB_YESNO, MB_OK etc | Windows |
| MinutesBetween | DateUtils |
| Now | SysUtils |
| OleInitialize | ActiveX |
| OleUninitialize | ActiveX |
| PItemIDList | ShlObj |
| POleCmd | ActiveX |
| POleCmdText | ActiveX |
| PostMessage | Windows |
| PosX | StrUtils |
| QueryHighPerformanceCounter | Windows |
| QueryPerformanceCounter | Windows |
| ReverseString | StrUtils |
| RoundTo | Math |
| SendMessage | Windows |
| SetForegroundWindow | Windows |
| ShellExecute | ShellAPI |
| ShellExecuteEx | ShellAPI |
| SHGetFileInfo | ShellAPI |
| SHFILEINFO | ShellAPI |
| ShowMessage | Dialogs |
| Sleep | SysUtils |
| StrAlloc | SysUtils |
| StrPas | SysUtils |
| StrToDate | SysUtils |
| StrToInt | SysUtils |
| StrToIntDef | SysUtils |
| TAdoConnection | ADODB |
| TAdoQuery | ADODB |
| TAlign | Controls |
| TAlignment | Classes |
| TAnchors | Controls |
| TBitmap | Graphics |
| TBlobStream | DBTables |
| TCanvas | Graphics |
| TClientSocket | ScktComp |
| TComboBox | StdCtrls |
| TComponent | Classes |
| TControl | Controls or QControls |
| TCriticalSection | SyncObjs |
| TField | DB |
| TFieldType | DB |
| TFileName | SysUtils |
| TFileStream | Classes |
| TForm | Forms |
| TFrame | Forms |
| TGroupBox | StdCtrls |
| TIID | ActiveX |
| TIniFile | IniFiles |
| TJPEGImage | Jpeg |
| TLabel | StdCtrls |
| TList | Classes |
| TMemo | StdCtrls |
| TMemoryStream | Classes |
| TMouseButton | Controls |
| TNofityEvent | Classes |
| TObjectList | Contnrs |
| TOSVersionInfo | Windows |
| TPanel | ExtCtrls |
| TPoint | Types |
| TProcessEntry32 | TlHelp32 |
| TProgressBar | ComCtrls or QComCtrls |
| TRadioButton | StdCtrls |
| TRadioGroup | ExtCtrls |
| TRect | Types |
| TRegistry | Registry |
| Trim | SysUtils |
| TRoundToRange | Math |
| TSearchRec | SysUtils |
| TSize | Windows |
| TSocketAddrIn | Winsock |
| TStaticText | StdCtrls |
| TStream | Classes |
| TStringList | Classes |
| TStrings | Classes |
| TStringStream | Classes |
| TSystemTime | Windows |
| TTable | DBTables |
| TTabSheet | ComCtrls |
| TThread | Classes |
| TTreeNode | ComCtrls |
| TWebBrowser | SHDocVw or SHDocVw_TLB |
| TWinSocketStream | ScktComp |
| TWMCommand | Messages |
| Unassigned | Variants |
| VarArrayCreate | Variants |
| VarArrayOf | Variants |
| VirtualProtect | Windows |
| WM_USER | Messages |
| YearOf | DateUtils |
|
TDBXPropertyNames |
DBXCommon |
| TIdTCPConnection | IdTCPConnection |
