SCREEN EDITOR

If you are using TDS-PC for Windows you may not ever need the TDS9092 full screen editor. Work with a word-processor in the PC instead. If you are using a dumb terminal then the full screen editor will be your main way of writing Forth source code.

Forth can be compiled interactively line by line or an editor can be used to format source code, which is then compiled. The latter has the advantage of keeping the source code for later modification and documentation. The TDS9092 has an editor designed to work with simple terminals or through the serial input-output port of a PC.

Interactive use is possible even with hand-held terminals. For the full screen editor the terminal should have an 80 x 24 screen and 2-character sequences which will send the cursor up, right and home. A code sequence is also needed to home and clear the screen. ASCII codes hex 08 and 0A are used for left and down.

There are 13 screens available. Screen 0 does not give an error but is not physically available. Do not use it. The screens act in the same way as disk on larger Forth systems. The operating software uses virtual memory to access them but this is not apparent to the user.

The screens are at addresses 8000 to B3FF, each one having 0400 bytes (1024 in decimal). The area B400 to BC07 comprises two virtual memory buffers. The applications program has all the RAM 8000 to BC07 (15K bytes) available since the editor is only used for program generation.

On power-up all the screens are disabled. To enable them you need to type $B400 06 +ORIGIN ! (see COLD START PARAMETER TABLE). The screens will be filled with random data, but a ctrl+B will blank the screen once you are in the editor. The reset button and RESET* signal in at the connector both give warm starts preserving source code and dictionary.

To enter the editor type 1 EDIT to enter screen 1, then type ctrl+B. After a moment a blank page is presented on which source code can be written and edited.

The cursor is in a box of size 64 characters 16 lines. These are the 1024 bytes of the Forth screen in memory. The bell marks any of the four limits.

If the full screen editor does not appear to work this is because the control codes in the Forth computer do not correspond with those needed by the computer or terminal. If using a PC type IBM return, otherwise see SETTING THE TERMINAL for details of how to change the codes.

FULL SCREEN EDITOR COMMANDS

The full screen editor control commands in the following table are available.

(UP ARROW)	Moves cursor up on screen. (ctrl+W sometimes)
(RIGHT ARROW)	Moves cursor right on screen. (ctrl+S sometimes)
(DOWN ARROW)	Moves cursor down on screen. (ctrl+Z sometimes)
(LEFT ARROW)	Moves cursor left on screen. (ctrl+A sometimes)
ctrl+B	BLANKS current screen to all spaces.
ctrl+E	ERASES current line to all spaces.
ctrl+I	INSERTS text held in PAD to the current line, moving down lower text.
ctrl+N	NEW SCREEN is selected according to number of current cursor line.
ctrl+O	OPENS up a gap. Lower text is moved down.
ctrl+P	PAD holds the current cursor line
ctrl+Q	QUITS editor and returns to interactive system.
ctrl+R	REPLACES the current line with that held in PAD.
ctrl+S	SCREEN re-listing. Current screen is displayed. (ctrl+L LIST used with some terminal code settings)
ctrl+T	TOP of the screen is selected. Cursor homes.
ctrl+W	WIPES out this line and moves up lower text. deleted is not lost, it is held in PAD. (ctrl+K KILL used with some terminal code settings).
ctrl+[	Moves rest of line one character left. The current character is deleted.
ctrl+]	Moves rest of line one character right. A space appears at the cursor position.
ctrl+-	Blank display and decrement screen no. Re-list with ctrl+S.
ctrl+\	Blank display and increment screen no. Re-list with ctrl+S.

3 5 COPY moves screen 3 to screen 5. This is used outside the editor, i.e. interactively. The up, down, left and right commands allow modification of text anywhere on the displayed screen. The return key moves the cursor to the start of the next line. When the source code is complete the editor should be left using ctrl+Q and compilation accomplished in the usual Forth manner, e.g.

4 LOAD compiles screen 4 (and successive ones as long as --> appears in the screen).

On error the abort point of the compiler can be easily found. WHERE re-enters the editor at the bad screen, and the cursor is placed where the compiler stopped. Note that the actual error may be at this point or a little way before it.

SETTING THE TERMINAL

When power is applied to the TDS9092 the system transfers 28 bytes of terminal information to RAM at locations BE10-BE2B. You can alter all the terminal parameters. The table under DUMB TERMINAL SUPPORT shows their addresses, values allocated at power-up and functions. Alternatively use any of the standard code sets built-in using the words shown later.

DEFAULT VDU CODES

ADDRESS	CONTENT	FUNCTION
BE10	0A	Key to send the cursor down
BE11	08	Key to send the cursor left
BE12	0B	Key to send the cursor up
BE13	0C	Key to send the cursor right
BE14	02	Key to blank current Forth screen
BE15	05	Key to erase current line
BE16	09	Key to insert line and move down
BE17	0E	Key to select new Forth screen
BE18	0F	Key to open up a gap and move down
BE19	10	Key to hold current line in pad
BE1A	11	Key to quit editor
BE1B	12	Key to replace line from pad
BE1C	13	Key to relist current editor screen
BE1D	14	Key to put cursor to top of screen
BE1E	17	Key to wipe out line and hold in pad
BE1F	1D	Key to move rest of line right
BE20	1B	Key to move rest of line left
BE21	1C	Key to blank terminal and increment screen no.
BE22	1F	Key to blank terminal and decrement screen no.
BE23	FF	Future use
BE24	001E	Pair of bytes to home cursor
BE26	001A	Pair of bytes to clear terminal screen
BE28	000B	Pair of bytes to send cursor up
BE2A	000C	Pair of bytes to send cursor right

For example if ESC R homes the cursor on your terminal then re-set location BE24 to these ASCII codes 1B and 52 as follows:

HEX 1B52 BE24 !

On changing command keys do not allocate the same code twice.

DUMB TERMINAL SUPPORT

The codes in the table above fit many terminals including ADM3A, Televideo, VC4604, etc., and they can be re-set at any time by typing STD . The next most popular code set is for Digital Equipment Corporation terminals. Just type VT52 if you have a VT52 or VT100 terminal and appropriate codes will be allocated.

This is a table of all the different terminal editor control sets built into the TDS9092. Remember that the only purpose is for use with the full screen editor and associated words UP DOWN RIGHT LEFT HOME PAGE . If you are not using the editor or any of these words you need not have the codes set correctly.

ADDR	STD	STDX	IBM	BBC	VT52	NY	V-C	ADDS	H1500	H1520	CIF
BE10	0A	1A	0A	0A	1A	0A	0A	0A	1A	1A	1A
BE11	08	01	08	08	01	08	08	08	01	01	01
BE12	0B	17	0B	0B	17	0E	1A	0B	17	17	17
BE13	0C	13	0C	0C	13	18	15	0C	13	13	13
BE14	02	02	02	02	02	02	02	02	02	02	02
BE15	05	05	05	05	05	05	05	05	05	05	05
BE16	09	09	09	09	09	09	09	09	09	09	09
BE17	0E	0E	0E	0E	0E	19	0E	0E	19	19	0E
BE18	0F	0F	0F	0F	0F	0F	0F	0F	0F	0F	0F
BE19	10	10	10	10	10	10	10	10	10	10	10
BE1A	11	11	11	11	11	11	11	11	11	11	11
BE1B	12	12	12	12	12	12	12	12	12	12	12
BE1C	13	0C	13	13	0C	13	13	13	0C	0C	0C
BE1D	14	14	14	14	14	14	14	14	14	14	14
BE1E	17	0B	17	17	0B	17	17	17	0B	0B	0B
BE1F	1D	1D	1D	1D	1D	1D	1D	1D	1D	1D	1D
BE20	1B	1B	1B	1B	1B	1B	1B	1B	1B	1B	1B
BE21	1C	1C	1C	1C	1C	1C	1C	1C	1C	1C	1C
BE22	1F	1F	1F	1F	1F	1F	1F	1F	1F	1F	1F
BE23	FF	FF	FF	FF	FF	FF	FF	FF	FF	FF	FF
BE24	00	00	00	00	1B	00	00	00	1B	1B	00
BE25	1E	1E	0B	1E	48	1D	19	01	12	12	19
BE26	00	00	00	00	1B	00	00	00	1B	1B	00
BE27	1A	1A	0C	0C	4A	1F	18	0C	17	1C	18
BE28	00	00	00	00	1B	00	00	00	1B	1B	00
BE29	0B	0B	1E	0B	41	0E	1A	1A	0C	0C	1A
BE2A	00	00	00	00	1B	00	00	00	1B	1B	00
BE2B	0C	0C	1C	09	43	18	15	06	10	10	15

The word BBC also sets cursor movement codes appropriate for Viewdata.

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