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                      GRAPHICS ON CP/M KAYPROS

                          by Peter Donnelly

                            January 1986

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     The graphics capabilities of the Kaypro are generally not well 
documented; indeed, buyers of the new Kaypro 1 might read the user's 
guide from cover to cover without obtaining the slightest hint that 
their machine has graphics at all. 
      The purpose of this article is to assemble some facts so that 
the reader can use the Kaypro graphics fully - at least, as fully as 
can be done without resorting to machine language. As far as I know, 
what is said here applies to all CP/M Kaypros manufactured since 
1984, and to earlier model 10s.

1. ESCAPE SEQUENCES

     Some screen functions are handled through escape sequences: that 
is, a string consisting of the ^[ character plus one or more other 
characters is sent to the screen. In MBASIC the sequence "ESCape, B, 
0" (as it appears in the Kaypro manual) would take the form:

     PRINT CHR$(27) + "B0"; 
or   PRINT CHR$(27); "B0";

When variable integers form part of an escape sequence they are 
sent in the form of the character having that ASCII decimal number. 
For example, to position the cursor at row R, column C, where the 
general form of the sequence is "ESC, =, row + 32, col + 32", you 
would use this command:

     PRINT CHR$(27) + "=" + CHR$(R + 32) + CHR$(C + 32);

Escape sequences can also be sent from the system prompt by pressing 
the ESC key followed by the appropriate letter keys, then RETURN. The 
system will echo the command to the screen, followed by a question 
mark, and as a result the escape sequence will take effect. This is 
handy when you break out of a program unexpectedly and find that your 
cursor has disappeared or that everything is still in inverse video, 
and you want to restore things to normal without a cold boot. (It's 
also handy - though this has nothing to do with graphics - for 
sending escape sequences to set up a printer. Just add ^P to the 
sequence.)

2. CONTROL CHARACTERS

     Certain control characters, when ordered to be printed to the 
CRT, will manipulate screen output; these are summarized in the 
appendix. They can be sent by a program, or like escape sequences 
they can be entered at the system prompt. For example, to clear the 
screen at the prompt just type CTRL-Z RETURN.
     Cursor movement through control characters is limited. You 
cannot backspace, for example, over an empty part of the screen; 
something has to have been printed there, if only spaces. 

3. CURSOR ADDRESSING

     The cursor can be sent to any point on the screen through the 
escape sequence mentioned in paragraph 1 above. 
     MBASIC has a peculiarity worth mentioning. Because there is a 
limit on how much it will handle as a string without a carriage 
return, you cannot just keep sending the cursor from one point to 
another with an input loop; if you do, MBASIC will respond by 
spitting out odd characters and line feeds. The solution is to insert 
into the loop another command like PRINT CHR$(30) (with no 
semicolon).
     Remember, every time the cursor prints a character it will 
advance. Thus the last column of row 24 is effectively off-limits if 
you want to preserve a whole screenful of graphics; when you print 
something there the cursor will try to drop down and thus force 
everything to scroll up a line.

4. STATUS LINE

     The so-called status line is the 25th line of the screen, and it 
is only accessible through direct cursor addressing. If you turn on 
"status line preservation," anything printed on the line will remain 
there despite whatever happens on the screen above, whether scrolling 
or clearing.
 
5. SPECIAL EFFECTS

     The four special video effects - inverse video, reduced 
intensity, blinking, and underlining - can be toggled on and off with 
escape sequences and can be used in any combination. They affect only 
what is printed while they are toggled on, and they apply to all 
characters, whether keyboard characters or graphics.
     The Kaypro has no true highlighting; the only way the effect can 
be emulated is to print most things at half-intensity and the 
"highlighted" strings at normal intensity. But of course this makes 
it necessary for the user to adjust his screen brightness control. 
     My own view is that half-intensity should never be used for text 
except in combination with inverse video. A number of programs, 
including a few commercial ones, use a combination of normal and 
half-intensity text to highlight key letters in menus and so on, and 
the result is less than satisfactory. Most people, I'm sure, have 
their screens adjusted so that normal text is comfortably readable, 
and at this setting half-intensity uninverted text almost disappears. 
(Particularly puzzling is TURBO PASCAL's installation for "Kaypro 
with highlight," where what ought to be highlighted is in fact 
printed at half-intensity; and if you turn your screen up to make 
these parts reasonably visible, everything else including the text on 
the editing screen becomes uncomfortably bright. While it's possible 
to modify this feature, the installation program doesn't allow a long 
enough escape sequence to set highlighting to half-intensity AND 
inverse.)

6. THE ASCII GRAPHICS

(A.) In addition to the ordinary keyboard characters, the Kaypro 
terminal is capable of displaying a number of graphics characters 
each occupying one "cell," the screen being made up of 25 by 80 such 
cells. All post-1984 machines have what might be called "block 
graphics" associated with the upper part of the ASCII set. Any of 
these graphics can be displayed by a simple command to send the 
character of the appropriate number to the screen, e.g. PRINT 
CHR$(255). 
     The characters are made up of eight pixels or tiny squares, each 
either green ("on") or black ("off"). These graphics can be seen as 
eight-bit binaries where the upper right corner is the least 
significant bit, the upper left the next most significant, and so on 
to the lower left corner, which represents the most significant bit, 
or 2 to the 7th power. A cell may be mapped as follows, with the 
numbers representing the amount added to the bit value of the 
character if that pixel is "on":

                          -----------
                          |  2 |  1 |
                          -----------
                          |  8 |  4 |
                          -----------
                          | 32 | 16 |
                          -----------
                          |128 | 64 |
                          -----------

     The first of the graphics characters is #128, a blank space, 
with a bit value of 0; the last is #255, which is lacking only the 
lower left corner and so has a value of the sum of the first 7 powers 
of 2, or 127. It is thus possible to derive the form of any of these 
graphics characters from its ASCII number, the bit value being the 
ASCII number minus 128. 
     Having reached the upper limit of the ASCII set without finding 
any characters which have the lower left corner filled in, we now 
have to go into inverse video, where we encounter another 128 
symbols, each the negative image of its counterpart and thus having 
the inverse (or ones complement) bit image; #128, for example, binary 
0000 0000, now becomes a full block whose on-bits, 1111 1111, total 
255. The bit value of each inverse character is 383 minus its ASCII 
number.
     The state of any pixel in a given graphics character can be 
determined by an arithmetic "and" test. Let "y" be the bit value of 
the character as determined from its ASCII number and the state of 
inverse video, let "x" be the power of 2 corresponding to the 
position of the pixel in question, and let "pixelon" be a Boolean 
returning "true" if the pixel is illuminated. The statement in Pascal 
would then take the form:

     if (x and y) > 0 then pixelon else not pixelon;

This determination is the key to writing a routine to translate the 
screen graphics into terms your printer can understand. (See section 
11 below.)

(B.)  The Kaypro video controller is capable of displaying a number 
of other graphics including thin horizontal, vertical, and diagonal 
lines, triangular blocks, and mathematical symbols. Each of these 
graphics is, again, associated with an ASCII number, this time in the 
range 0-31. (One of the triangles also shows up mysteriously as #127, 
the DEL character.) 
     Unfortunately, these graphics won't always appear on demand. To 
begin with, your programming language may interpret a character in 
this range as a control code. MBASIC, for example, always treats 
CHR$(9) as a horizontal tab. (Ever notice that you can't use it as 
part of an escape sequence in an MBASIC printer set-up?) Second, the 
operating system itself may also insist on treating certain 
characters as control codes (e.g. #7 as a bell, #13 as a carriage 
return). 
     In the Kaypros running CP/M 2.2u it appears that ALL characters 
in the lower range are scooped up before reaching the screen, even 
those that have no active control function. A command like PRINT 
CHR$(1) produces nothing at all.
     On "older newer" models like my '84 2X it's possible to print 20 
or so of these low-range characters with simple "write" commands in 
Pascal, and most of these are also accessible through MBASIC. I can 
also conjure them up by typing the matching control code at the 
system prompt and pressing RETURN. But there's no way to coax out the 
graphics that lie behind active control codes like ^G, ^J, ^M, and 
^Z.
     It is a frustrating situation for the programmer. One could have 
hoped for a simple escape sequence that would somehow disable the 
control codes and allow the full potential of the video chip to be 
exploited. However, if such a sequence exists it is a well-kept 
secret. Consequently if you want to see the full menu of Kaypro 
graphics, or use them, you'll have to turn to the KBOARD segment of 
the commercial program REMBRANDT (by DG Systems), which accesses them 
by doing an end-run around the BIOS and taking direct control of the 
video chip. Where the capable author of that program has gone I dare 
say not many will follow.


7. PIXEL GRAPHICS

     Since each block graphics character is made up of 4 rows and 2 
columns of pixels, the screen may be seen as an array of 100 by 160 
pixels, and with the appropriate escape sequence we can fill in any 
individual pixel on the screen. 
     The terminal is not actually printing every pixel location 
independently; it's really just assigning an ASCII block graphic to 
each cell of eight pixel locations and changing it whenever a pixel 
is added or taken away. For the programmer this doesn't make a great 
deal of difference, but you will notice that a pixel is printed in 
half-intensity when it is plunked down among half-intensity 
neighbors. You will also find that pixels can't be printed in a cell 
where there is already a keyboard character, even if there wouldn't 
be any actual overlap.

8. VIDEO MODE

     So far all I've been able to discover about video mode is that 
when it's turned on you must print a graphics character twice, or two 
graphics characters in succession, before anything appears on the 
screen. Then what you see is the first character printed normally, 
and the second character superimposed with the bits "swapped"; i.e. 
the value of the least significant bit is traded for the most 
significant, and so on. Thus #129 (upper right bit "on") and #255 
(lower left bit "off") can be printed together to make a solid block, 
and indeed all the block graphics with the high bit (lower left 
corner) "on" can be generated by superimposing a "swapped" #129 on 
the ASCII characters from #128 to #255. This is another way of doing 
what one can do with inverse video; whether it has any advantages I 
cannot say.

9. THE TYPE COMMAND

     The TYPE command will read any text file, and text files can 
include graphics and escape sequences. 
     Most word-processing programs won't normally allow the insertion 
of non-keyboard characters into text. You can sneak them in with 
Xpert Software's XTRAKEY, which allows you to turn any keyboard 
character into a block graphic by setting the high bit "on," i.e. 
adding 128 to the ASCII number. The graphics won't show up within the 
word-processing program, but they will be TYPEable. (WordStar users 
must go into non-document mode to prepare TYPEable files, since 
document mode uses the high bit for its own purposes.) 
     For portability, TYPEable files and indeed any graphics routines 
shouldn't include characters that might not show up on another 
machine such as the Kaypro 1 - namely the phantom graphics from the 
lower part of the ASCII set. On such machines these characters will 
not even show up as spaces; rather nothing at all will be printed, 
and so the alignment of columns will be thrown out of whack.

10. GRAPHICS UNDER ZCPR

     The alternative operating system ZCPR disables the Kaypro 
graphics, and while there is a command to re-enable them, helpful 
programmers can save the user the trouble by poking the byte FF into 
location 004F at the beginning of any graphics routine, and restoring 
the value 00 at the end. There appears to be no conflict with CP/M.

11. PRINTING GRAPHICS

     It would be nice if you could print any graphics character just 
by sending the appropriate ASCII number to the printer, but 
unfortunately this is not the case. Most dot-matrix printers have 
italics and international characters associated with the upper half 
of the ASCII set; if there is an alternative graphics set, it will be 
for the IBM system. 
     Consequently, to print the Kaypro block graphics you must put 
the printer in "graphics mode" and define which pins are to be fired 
at each impact. This means breaking the graphic character into its 
two component columns and examining each of these for "on" pixels, 
then converting the bit-sum of the column into the byte required by 
your printer so that it knows which pins to fire as it prints that 
column. How many pins you will use for each pixel, and how many times 
they will be fired, will depend on the size and proportions of the 
desired result. For example, using standard density graphics on the 
Epson - 480 dots per line - to reproduce the full width of the screen 
(160 pixel columns) as the full width of the paper, the pins would be 
fired 3 times for every column, and 2 of the 8 pins would be used for 
each "on" pixel.
     As for the graphics in the lower part of the ASCII set, they 
would presumably have to be individually designed as "downloadable 
characters" - a large task - and then downloaded to the printer to be 
printed in text mode. 

12. AVAILABLE SOFTWARE

     At least three commercial and two non-commercial drawing 
programs are now available for the Kaypro. I will describe briefly 
those I've had experience with. 

SCS-DRAW (Second City Software, Box 267960, Chicago IL 60626)

     A very likeable program for designing images to be printed to 
paper. Drawing is done in black on a large green canvas of 336 x 362 
pixels, a portion of which is displayed in a window that occupies 
about two-thirds of the screen, the rest being taken up by a menu and 
window-position indicator. While inversion is used to good effect 
(you can draw a line that shows black against green and green against 
black), every pixel is simply either on or off, and hence there are 
no real video effects like half-intensity or blinking. A nice touch 
is that you can draw or erase a single pixel without leaving "move" 
status, saving much confusion. Text can be added in a choice of 
rudimentary fonts and enlarged to as much as banner size. There are 
many other features including cut-and-paste, merging of images in 
various ways, automatic drawing of lines, circles, and rectangles, 
easy block erase, rapid cursor moves, pattern-fill, and on-screen 
enlargement in two separate dimensions. Options at the printing stage 
enable further enlargement, flipping, rotating, and repeating of 
images. The program is helpful, quick, and easy to use throughout. 

REMBRANDT (DG Systems, 22458 Ventura Bvd., Ste. E, Woodland Hills, CA 
91364)

     REMBRANDT is both screen- and printer-oriented, a good all-round 
program that is the only one to exploit all the graphics capabilities 
of the Kaypro. Drawing is done with the entire ASCII set - all 256 
characters - on a full-screen canvas. You have 10 graphics characters 
on your "palette" at one time, choosing one by striking a number key 
- painting by numbers, as it were. Ordinary keyboard characters can 
be typed in anytime. Access to the fine-line graphics makes possible 
much more varied effects than the block graphics allow, such as 
graphs that look like they're drawn on graph paper. Screens can be 
chained together for presentation in a "slide-show" format with 
various effects such as fade-in. Auxiliary programs will prepare 
various types of graphs automatically from entered data. REMBRANDT 
puts out good printed images, and reproduces half-intensity on paper 
as well as on the screen, but as a printing program it is less 
flexible than SCS-DRAW; nor is the overall presentation as attractive 
and fast-moving. 

DDRAW (non-commercial; available from many sources)

     This pioneer program uses pixel drawing and keyboard characters 
on a full-screen canvas. Features include automatic drawing of 
circles, lines, and rectangles and filling of enclosed areas. All the 
video effects are available; they are added to blocks after they have 
been drawn. The cut-and-paste routine is limited to smallish areas 
with no text, but you can store up to four details (called 
subpictures) in memory to be shuffled about at will. An optional 
status line keeps track of the cursor position and the drawing/ 
erasing/moving status, and there is a separate screen giving a menu 
of commands. Files can be saved in TYPEable format, something that is 
not true of either of the commercial programs reviewed. DDRAW fully 
supports the Gemini printer; my Panasonic (a machine similar to the 
Epson) will print the graphics small but not text and graphics 
combined.

ARTIE (non-commercial; if all else fails, send me a postal money 
order for $5 at the above address)

     My own entry into the field. ARTIE uses the ASCII graphics, 
including (on machines where they are TYPEable) some from the lower 
range. Graphics can be chosen from a palette above the canvas or from 
a separate menu. You can cover the canvas more quickly than with 
DDRAW, but that program is better for detailed sketching. (DDRAW 
files can be read into ARTIE screens, so it's possible to have the 
best of both programs.) The canvas is only 20 lines but an auxiliary 
program links two files to make a 24-line display. Details can be cut 
and moved or written to file, then read back into the screen with 
various video effects added. Rapid fill and empty functions; disk 
logging and directory of relevant files; five help screens as well as 
status-line reminders; a toggle for the keyboard clicker - ARTIE is 
definitely built for comfort, which is why it weighs in at 50k or so 
on disk. So far the Panasonic and Diablo/Juki printers are supported, 
but the emphasis is on preparing screen displays.

     By the way, the Juki printer that has been distributed with 
many Kaypros is supported by SCS-DRAW and REMBRANDT as well as ARTIE. 
The process may be painfully slow, noisy, and ribbon-consuming, but 
your daisy-wheel printer CAN produce some very good graphics. 

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                              APPENDIX 

         ESCAPE SEQUENCES, CONTROL CODES, AND PORT COMMANDS

Cursor left                        ^H    ASCII 7 decimal
Cursor right                       ^L         12
Cursor down                        ^J         10
Cursor up                          ^K         11
Erase from cursor to end of screen ^W         23
Erase from cursor to end of line   ^X         24
Clear screen                       ^Z         26
  (also cancels special effects)
Home cursor                        ^^         30

The following are all preceded by ESC, character #27:

Insert line                        E     | contrary to  
Delete line                        R     | manuals 
Inverse video on/off               B0/C0
Reduced intensity on/off           B1/C1
Blinking on/off                    B2/C2
Underlining on/off                 B3/C3
Cursor visible/invisible           B4/C4
Video mode on/off                  B5/C5   
Remember/recover cursor position   B6/C6
Status line preservation on/off    B7/C7
Cursor address                     =, row + 32, col + 32

Where row and col refer to the matrix of 100 by 160:

Print pixel            *, row + 31, col + 31
Erase pixel            #32 (space), row + 31, col + 31
Print line             L, row1 + 31, col1 + 31, row2 + 31, col2 + 31
Erase line             D, row1 + 31, col1 + 31, row2 + 31, col2 + 31

The following two commands are shown in their MBASIC format:

Stop cursor blinking     OUT 28, 10: OUT 29, 0
Turn cursor to underline OUT 28, 10: OUT 29, 15* 
                         (* or 79 or 111 for blink rate)

In Pascal these commands would take the form port[28]:= 10; etc.

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                             POSTSCRIPT 

I would like to offer my thanks to those who have shared their 
knowledge of this somewhat obscure subject; I will not name them, 
because the mistakes here are all my own. Corrections and additions 
will be most welcome at the above address.

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