The refinement discussed here so far, is implemented in the
overall structure of the program:


                 Operations   -------------X
                                        Screen(s)
                 Protocol              /  |
        Shell X------------X Emulation    |
                                       \  V
                                        Widget
                 Events X------------------
                                         

Part    Application  Protocol      Data model   Visualization
                                                User Events

Files   TEShell.C    TEmulation.C  Screen.C     TEWidget.C
                     TEVt102.C

Types   TEShell      Emulation     TEScreen     TEWidget



The abstract data type, in which the text is represented and
manipulated by a set of operations is 


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On the first glance, the terminal consists of the following
parts:

- A screen to display characters to the user on a rectangular area.
- A keyboard to accept the user keypresses.
- A bidirectional serial connection, on which the application
  sends the text to be displayed to the terminal and on which
  the user's key pressed are forwarded to the application.
- The application that actually run on the terminal.

More formally our terminal model consists of
- a character screen : a matrix [Lines,Columns] -> Character
- a current visual pointer position (cursor).
- a set of operations by which the screen can be manipulated
- a set of events (mainly keystrokes)
- two streams on which bytes are exchanged between the
  application and the terminal which are used to communicate
  the operations and events between the two end points.
- an initial state.

           0       (columns)     V--- Columns-1
          +-----------------------+
          |                       | 0
          |  text on              |
          |  the screen           |
          |                       | (lines)
          |                       |
          |                       |
          |                       | Lines-1
          +-----------------------+


For adressing purpose, we call the (columnNo,lineNo) pair a "position"

- protocol == collection of operations and their encoding.

Beschreibung

- Strom von Kommandos und Anfragen
- Strom von Ereignissen und Antworten

- HostToTerminalStream
  : Sequence(Command U Request)

- Type Command-Tokens
  : Prn(Char)                            - literal(Character) - 1 char subset
  : Ctl(Char)                            - 0-parm command
  : Esc(Char)                            - 0-parm command
  : Csi(Char,Args)                       - fix & flex num parm command
                                           - some are sub-commands
  : Pri(Char,Args) <: Csi("?",Char,Args) - fix & flex num parm command
                                           - some are sub-commands
  : Hsh(Char)                            - 0-parm command
  : Scs(A,B)                             - 2-parm num command
  : Vt5(A,B)                             - 2-parm num command

- command definition

  : name(parm:Type<:Integer)

  : setFgColor(color)
  : setBgColor(color)
  : setReverse(bool)
  : setBold(bool)
  : setBlink(bool)

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