RTL class hierarchy

TObject
- Exception Base class of all exceptions.
  - EAbort Abort error.
  - EAbstractError Abstract error.
  - EArgumentException Invalid argument passed to a function.
    - EArgumentNilException Exception raised when a required argument is Nil.
    - EArgumentOutOfRangeException Argument out of valid range passed to a function.
    - EInOutArgumentException
  - EAssertionFailed Assertion failed error.
  - EBitsError Exception raised when an error occurs in a method of .
  - ECFError
  - EComponentError Exception raised when an error occurs in the component registration routines.
  - EConvertError Conversion error.
  - EDateTimeException
  - EDirectoryNotFoundException Exception raised when a directory is not found.
  - EEncodingError Exception raised by the TEncoding class.
  - EExternal External Exception.
    - EAccessViolation Access Violation error.
      - EBusError Bus error exception.
    - EControlC Control-C (abort) was pressed on the console.
    - EExternalException External exception.
    - EIntError Integer operation error.
      - EDivByZero Division by zero error.
      - EIntOverflow Integer overflow error.
      - ERangeError Range check error.
    - EMathError Mathematical error.
      - EInvalidArgument Exception raised when invalid arguments are passed to a function.
      - EInvalidOp Invalid operation.
      - EOverflow Float overflow error.
      - EUnderflow Float underflow error.
      - EZeroDivide Division by zero error.
    - EPrivilege Privileged instruction error.
    - EStackOverflow Stack overflow error.
  - EFileNotFoundException Exception raised when a file is not found.
  - EFormatError Formatting error exception.
  - EHeapMemoryError Heap memory error.
    - EInvalidPointer Invalid pointer operation.
    - EOutOfMemory Out of memory error.
      - EOutOfResources Exception raised when the system is out of resources.
  - EInOutError Input/Output error.
  - EIntfCastError Invalid interface cast error.
  - EInvalidCast Invalid typecast error.
  - EInvalidContainer Invalid container error.
  - EInvalidInsert Invalid insert error.
  - EInvalidOperation Exception raised when an invalid operation is performed. Obsolete.
  - EInvalidOpException Invalid operation exception.
  - EListError Exception thrown when a list-related error occurs.
  - EListError
  - ELocalTimeInvalid
  - EMonitor
    - EMonitorLockException
    - ENoMonitorSupportException
  - ENoConstructException Error raised when instantiating a TCharacter class.
  - ENoDynLibsSupport No dynamic library support.
  - ENoThreadSupport No Thread support error.
  - ENotImplemented Exception raised in case of a not implemented feature.
  - ENotSupportedException Exception raised when a feature is not supported.
  - ENoWideStringSupport Exception raised if no widestring support is available in the executable.
  - EObjectCheck A Nil object reference was encountered.
  - EObjectDisposed
  - EObserver Error raised when an observer error occurs.
  - EObserverException
  - EOperationCancelled
  - EOSError Operating system error.
  - EPackageError Package error.
  - EParserError Exception raised when an error occurs during the parsing of streams.
  - EPathNotFoundException Exception raised when a path is not found.
  - EPathTooLongException Exception raised when a path name is too long.
  - EProgrammerNotFound Delphi compatibility exception.
  - EPropertyConvertError Exception raised when converting a property.
  - EPropertyError Exception raised in case of an error in one of the functions.
  - EPropReadOnly Read-only property error.
  - EPropWriteOnly Write-only property error.
  - EResNotFound Exception raised when a resource, needed to initialize a component, is not found.
  - ESafecallException SafeCall exception.
  - ESigQuit Quit signal was received.
  - EStreamError Exception raised when an error occurs during read or write operations on a stream.
    - EFCreateError Exception raised when an error occurred during creation of a stream.
    - EFilerError Exception raised by the component streaming system if an error occurs.
      - EClassNotFound Exception raised when an unknown class is referenced in a streamed component.
      - EInvalidImage Exception raised when the resource header needed for streaming of a component is invalid.
      - EMethodNotFound This exception is no longer used.
      - EReadError Exception raised if an error occurs while reading from a stream.
      - EWriteError Exception raised when an error occurs during writing to a stream.
    - EFOpenError Exception raised when an error occurred during creation of a .
  - EStringListError Exception raised when an error occurs in a method of .
  - EThread Thread error exception.
    - EThreadDestroyCalled Exception raised when a thread is destroyed illegally.
    - EThreadExternalException Exception raised when an invalid operation is attempted on an external thread.
  - EThreadError
  - EVariantError Variant error.
    - EVariantArrayCreateError Error raised when a problem is detected during creation of an array.
    - EVariantArrayLockedError Error raised when an operation on a locked array is performed.
    - EVariantBadIndexError Error raised when an invalid array index is detected.
    - EVariantBadVarTypeError >Error raised when an invalid variant type is detected.
    - EVariantDispatchError Exception raised in case of variant dispatching errors.
    - EVariantInvalidArgError Error raised when an invalid argument is detected.
    - EVariantInvalidOpError Error raised when an invalid operation is performed.
      - EVariantInvalidNullOpError Variant invalid null operation error.
    - EVariantNotAnArrayError Error raised when an array operation is performed on a non-array variant.
    - EVariantNotImplError Error raised when a variant operation not implemented.
    - EVariantOutOfMemoryError Error to signal an out-of-memory condition.
    - EVariantOverflowError Error raised when an overflow error is detected.
      - EVariantRangeCheckError Exception class to signal range checks.
    - EVariantParamNotFoundError Error raised when a parameter is not found.
    - EVariantTypeCastError Error raised when an invalid typecast is performed.
    - EVariantUnexpectedError Exception raised during unexpected error.
  - TMREWException Exception used in TMultiReadExclusiveWriteSynchronizer.
- TAbstractObjectReader Abstract driver class to read stored component data.
  - TBinaryObjectReader Driver class descendant which reads component data stored in binary format.
- TAbstractObjectWriter Abstract driver class for writing component data.
  - TBinaryObjectWriter Driver class which stores component data in binary form.
  - TTextObjectWriter Driver class which stores component data in text format.
- TAggregatedObject Aggregated object.
  - TContainedObject Base class for contained objects.
- TAnsiStringBuilder Ansi-string version of string builder.
- TBasicActionLink Link between actions and action clients (e.g. controls).
- TBitConverter
- TBits Class to store collections of bits (binary values that can be 0 or 1).
- TCharacter Character operation.
- TCollectionEnumerator Implements IEnumerator for the TCollection class.
- TComponentEnumerator Implements IEnumerator for the TComponent class.
- TCustomAttribute
  - ComponentPlatformsAttribute
  - ObservableMemberAttribute
  - StoredAttribute
  - TUnimplementedAttribute
- TCustomVariantType Base class for a custom variant type.
  - TInvokeableVariantType TCustomVariantType descendent that implements DispInvoke.
    - TPublishableVariantType TInvokeableVariantType descendent that implements reading published properties.
- TEncoding Encoding support.
  - TMBCSEncoding Multi-Byte character set encoding.
    - TUTF7Encoding UTF-7 Unicode encoding.
      - TUTF8Encoding UTF-8 Unicode encoding.
  - TUnicodeEncoding UTF-16 Unicode encoding.
    - TBigEndianUnicodeEncoding Big-endian UTF-16 Unicode encoding.
- TFiler Class responsible for streaming of components.
  - TReader Generic reader object which reads component data from any given source.
  - TWriter Object to write component data to an arbitrary format.
- TFPGListEnumerator Generic list enumerator.
- TFPList Class to manage collections of pointers.
- TFPListEnumerator Implements IEnumerator for the TFPList class.
  - TListEnumerator Implements IEnumerator for the TList class.
- TFPSList Basic list of memory blocks.
  - TFPGInterfacedObjectList Generic interfaced object list.
  - TFPGList Generic list.
  - TFPGObjectList Generic object list.
  - TFPSMap Basic map object, used in generic maps.
    - TFPGMap Generic map.
    - TFPGMapInterfacedObjectData Generic map for reference counted objects.
    - TFPGMapObject Generic map.
- TInterfacedObject TObject descendent implementing the IUnknown interface.
  - TInterfaceList Standard implementation of the IInterfaceList interface.
  - TInterfaceThunk
  - TMultiReadExclusiveWriteSynchronizer Standard implementation of a IReadWriteSync interface.
  - TSimpleRWSync Read/Write synchronizing object.
  - TStreamAdapter Implements IStream for TStream descendants.
- TInterfaceListEnumerator Implements IEnumerator for the TInterfaceList class.
- TLinkObservers
- TList Class to manage collections of pointers.
- TMarshal
- TNoRefCountObject
- TObserverMapping
- TObservers
- TParser Class to parse the contents of a stream containing text data.
- TPersistent Base class for streaming system and persistent properties.
  - TCollection Base class to manage collections of named objects.
    - TOwnedCollection TCollection descendant which maintains owner information.
  - TCollectionItem Basic object that is managed by a class.
  - TComponent Base class for all components that need owner-owned functionality.
    - TBasicAction Abstract base class for all Actions.
    - TDataModule Container for non-visual components.
  - TInterfacedPersistent TPersistent descendant which implements the IInterface interface.
  - TStrings Class to manage arrays or collections of strings.
    - TStringList Standard implementation of the class.
- TRecall Helper class for storing published properties.
- TStream Base class for streams.
  - TCustomMemoryStream Abstract stream that stores its data in memory.
    - TMemoryStream Standard implementation of a stream that stores its data in memory.
      - TBytesStream Stream of bytes.
        TRawByteStringStream TBytesStream descendent with some single-byte string methods.
        TStringStream Stream that stores its data in a string.
    - TResourceStream Stream that reads its data from a resource object.
  - THandleStream Base class for streams that are identified by an OS handle.
    - TFileStream Stream that stores its data in a named file on disk.
  - TOwnerStream Stream which uses a second stream as a source.
  - TProxyAggregateStream
  - TProxyStream Proxy stream for the IStream interface.
- TStringsEnumerator Implements IEnumerator for the TStrings class.
- TThread Abstract Thread class.
- TThreadList Thread-safe list object.
- TTimeZone
- TUnicodeStringBuilder Ansi-string version of string builder.

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.