出现的问题：
在编译delphi程序时出现提示为：
[Error] MyUnit.pas(LL): Undeclared identifier: 'NNNN'
其中：
MyUnit.pas源文件的名称. LL第几行. NNNN提示的标识名.
原因：
编译器不能识别'NNN'这个标识。这可能是拼写错误或找不到定义文件造成。
解决方法：
- 常见的错误是由于拼写错误造成，例子如下：
var number: Integer;
begin
numbr := 1;
begin
numbr := 1;
变量定义为number，但使用时写成了numbr，将变量改正就可以。
- 另一种是代码正确，但要用到的单元没有包含进去。如：
try
.
.
except
on E: Exception do
.
[Error] Undeclared identifier: 'Exception'
.
.
except
on E: Exception do
.
[Error] Undeclared identifier: 'Exception'
代码是正确，但没有包含“sysutils”。下面的表格列举了一些类型和函数用到的单元。
Type Unit _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