33:
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be displayed either with the cells joined together, as with the existing quadrant characters, or with a narrow space between cells. A teletext emulator could interpret the control character U+001A ("separated graphics") to display space between cells, or U+0019 ("contiguous graphics") to revert to the default, joined appearance
899:
The word "sextant" is used in this document, by analogy with "quadrant"—a term used for certain UCS characters since 1999—to refer to a semigraphics block consisting of six smaller blocks or "cells" arranged in two columns and three rows. In the teletext specification, characters in this group could
519:
Some of the systems that had a programmable font set, but did not have a real high resolution raster graphics hardware, came with default character sets to be uploaded in character set RAM, and these sets often incorporated the ideas mentioned here, although it was often also the case that dedicated
253:
Sometimes the number of characters in the font, dedicated to block graphics, could be halved if the system also supported an "invert" attribute, as half the characters in a full block graphics font set are the logical inverse of the other half of the font set. Other tricks that were used to decrease
214:
Sometimes the text semigraphical characters are simply incorporated into the systems font-set, sometimes special video hardware is used to directly convert the bit-pattern from video memory into the pixels. In rare cases a character matrix was not dividable vertically by three, for example in an 8×8
226:
where the only way to get discrete pixels on the screen that could be turned on and off individually, (all points addressable) was by the use of a 2×3 pixel matrix of block graphics. In the case of the TRS-80 these block graphics were not incorporated into a font ROM, as later became the norm, but
183:
For example, an 8×12 pixel character could be divided vertically in two halves and horizontally in three parts, and then assigning "ink" and "background" values to the elements of the matrix in a binary pattern, corresponding to the binary sequence of the position in the font table of a
302:
also supported block graphics as well as "real" higher-resolution graphics. In addition, on the
Spectrum the system font (stored in its ROM) could be easily and instantly changed to one stored in RAM, allowing programmers to define their own semigraphical characters to suit their
314:. The latter supported not just 2×2 matrix semigraphics but also 2×3 matrix semigraphics, albeit imperfectly, as the semigraphics pixels in a character's middle row were less tall than those in the top and bottom rows, due to imperfect division of the 8×8 pixel character matrix.
254:
the number of needed characters, was to use a space for the "all bits are zero" character, and to use character 7F hex for the "all bits are on" character, as character 7F hex (decimal 127) was often defined as an "all pixels on" character (this was because when using
435:
only supported four colors in its high-resolution graphics mode, but in text mode it could display 16 different colors. Although the CGA adapter's font ROM did not contain all of the otherwise typical text semigraphics characters, it was still possible to create a
516:, which had no high-resolution graphics, nor reprogrammable characters, but relied fully on an extended font set with many pseudo graphical characters. With these it was still possible to generate games that looked like the system had high-resolution graphics.
466:
PETSCII Chart as displayed on the C64 in shifted and unshifted modes. (Not shown are control codes, as well as characters in the $ C0–$ FF range, which are the standard uppercase keycodes returned from the keyboard, and which are mirrored to the range $ 60–$
659:
character set, which replaced flashing uppercase characters when enabled. Although these Apple systems did not rely on these character sets they did play a role in simulating GUI like graphics of their more advanced family members, while still in text
419:
managed to combine normal text with a full set of 256 text semigraphical "characters" in a 2×4 matrix; the system distinguished the set of 256 semigraphics patterns from the 256-character set used for "normal" fonts via character
129:
from the moment it is turned on, even when no operating system is yet loaded. Single and double lines are still often drawn with this method when the system uses text mode; for example when running the BIOS setup program.
595:
relied completely on its character set for games, even though it was marketed through toy-shops. It never became a commercial success partly because of this limitation, which was outdated at the time (see
486:
are also characters in a font that are intended to give the impression that a system can support high resolution graphics, while in fact the system operates in text mode. Characters such as
45:
298:, where a matrix of 2×2 pixels was used, with the space and invert attribute tricks to keep the number of characters in the ROM needed down to just 7 (of the necessary 16). The
509:
font set. The original PET relied to such a degree on these characters that it printed them on its keyboard, as can be seen here, an example that other systems soon copied.
1157:"At the starting position of semigraphics mode, once the relevant attribute bit is set to one, a dot pattern will be written to the VRAM for the character code instead ."
357:
systems used a 2×3 matrix and one foreground ("ink"), and one background color, normally out of a set of eight colors (including black and white). Many systems used "
863:
250:
as the color of a pixel could not be changed on a per pixel basis, but only to one "ink", and one "background" color for all pixels within a character position.
1155:(Source in Japanese; the relevant sentence is "アトリビュートに開始位置とセミグラフィック指定ビット=1 を立てて、テキスト VRAM には文字コードの代わりにドットパターンを書き込みます。" This roughly translates to
880:
618:
series of computers offered no high resolution or programmable characters, but did have a very complete set of semigraphical characters (see
246:
If the system also supported color, the color resolution of the resulting pixels was normally equal to the text resolution, often leading to
1113:
1010:
1289:
884:
1083:
1054:
695:
835:
870:; Silva, Eduardo Marín; Mårtenson, Elias; Shoulson, Mark; Steele, Shawn; Turner, Rebecca (2019-01-04). "5. Graphic characters".
576:
relied on block graphics characters for a low-resolution graphics of 64×48 pixels black-and-white or 32×48 in black, white, and
773:
87:
with all binary combinations of a certain subdivision matrix of the text mode character size; this method is referred to as
1279:
231:. An earlier system using the same pseudo-graphics array of a 2 by 3 matrix was the Video Terminal Interface (VTI) of the
79:
There are two different ways to accomplish the emulation of raster graphics. The first one is to create a low-resolution
811:
437:
1191:
644:(clone of the popular Ohio Scientific superboard) also was a very early system that relied on its 256 characters set.
558:
was one of the first systems to rely heavily on semigraphical characters, to get any form of graphics on screen (see
813:
ETS 300 072 - Terminal
Equipment (TE); Videotex presentation layer protocol Videotex presentation layer data syntax
495:
150:
227:
were generated directly from the logic pattern of six bits from the video RAM using a dedicated circuit made from
236:
185:
1294:
537:
358:
37:
17:
199:. Less often used versions use a 1×6 "matrix", in which case these six "pixels" are sometimes referred to as
720:
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634:
138:
32:
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608:
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to use "rub-out" for a character square filled with "ink", which was often used to represent the cursor.
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One of the first systems that used such characters, the canonical example that others followed, was the
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759:
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102:(letters and figures) that appear as if drawn in raster graphics mode, sometimes referred to as
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953:. See the second image from above. The image shows small difference in height of some "pixel"s
80:
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graphics mode is an example, although with a 4:5:4 scheme the distortion effect was minimal.
169:
84:
49:
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Examples of systems that relied heavily on semigraphical characters for their graphics are:
871:
216:
1134:
512:
Another good example of a system that relied on semigraphical characters is the venerable
8:
1213:
1075:
1046:
932:
117:
Semigraphical characters (including some block elements) are still incorporated into the
1214:"old-computers.com Entry on the Sharp MZ80K mentions the lack of graphics capabilities"
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1028:
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punching out all seven holes, created the 7F hex "byte" which was considered to be the
208:
513:
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matrix the mosaic is sometimes divided so that it uses a 3:2:3 scan line scheme. The
604:
427:
One of the last video systems where text semigraphics were a useful option was the
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are good examples of systems using 2×2 matrix color semigraphics. But their
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character set. The PET was also one of the first systems to rely heavily on
951:"OLD-COMPUTERS.COM Museum ~ GALAKSIJA Galaksija software & screenshots"
607:
also used semigraphical characters in combination with block graphics (see
491:
405:
337:
177:
1260:"Games on the MZ-80K relied on its great set of semigraphical characters"
819:. European Telecommunications Standards Institute (published 1996). 1990.
626:
409:
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146:
1241:
873:
Proposal to add characters from legacy computers and teletext to the UCS
286:
Other examples of systems that relied on the use of block graphics are:
44:
27:
Method used in early text mode video hardware to emulate raster graphics
984:
859:
228:
118:
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173:
69:
781:. European Telecommunications Standards Institute. 1997. p. 6.
675:
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354:
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168:
Sample character set display showing block graphics as used in the
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also had a few characters to support 2×2 text semigraphics in its
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of the rub-out character (to the code point 127) led designers of
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The text modes of later Apple II computers, beginning with the
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without having to implement the logic for such a display mode.
1193:
Commodore C64 Manual: Commodore 64 Programmers
Reference Guide
369:). Other systems which used "Videotex"-like graphics are: the
858:
705:
263:
200:
933:"JayceLand's Weekly Rochester Events #191: All White Sixel"
573:
569:
164:
1136:
EF9345 - HMOS2 SINGLE CHIP SEMI-GRAPHIC DISPLAY PROCESSOR
122:
985:
Technical details ZX-81 character set and block graphics
273:
449:
347:
also supported a little used 6-block semigraphics mode.
203:. But dividing an 8×8 character in 2×2 "pixels" called
133:
Many of these historical ideas have been adopted into
794:
The
Unicode Standard, Version 15.1 - Geometric Shapes
498:
such as triangles gave such systems that appearance.
479:
has semigraphical characters indicated for easy entry
622:). - and so still offered many visually nice games.
494:like ♠, ♣, ♥ and ♦, and "graphical building block"
98:The second one is to use special shapes instead of
306:Other systems that used a 2×2 matrix included the
520:semigraphical characters were defined as needed.
1271:
1103:
524:Systems that relied on semigraphical characters
361:". One of the best known examples is the Acorn
881:International Organization for Standardization
222:The seminal use of this technology was in the
823:
326:
125:compatible video card, so any PC can display
854:
852:
1142:. SGS-THOMSON Microelectronics. March 1995.
757:
540:offered no form of graphics other than the
453:Semigraphical characters used on the game
444:
1206:
1104:Hervier, Carl; Vanlierde, Stéphane (204).
1230:. 2010-01-29 – via www.youtube.com.
1162:
849:
829:
404:graphic chip, only capable of displaying
1252:
1234:
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1021:
978:
925:
696:List of home computers by video hardware
470:
461:
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329:, to get any form of graphics on screen.
277:
163:
43:
31:
431:(CGA). This graphics adapter for early
14:
1272:
972:"Description of TRS-80 block graphics"
207:was also common (it was, for example,
1242:"Mattel Aquarius Homecomputer system"
1220:
1153:PC-8801 Programing - VRAM Information
989:
964:
274:Examples of the use of block graphics
1127:
1029:"R.T.Russell: BBC BASIC for Windows"
760:"Teletext separated mosaic graphics"
741:"R.T.Russell: BBC BASIC for Windows"
505:, which had many of them within its
438:160 × 100 CGA text semigraphics mode
282:Text block graphics set of the ZX-81
68:is a primitive method used in early
997:"CoCo Semi-graphics-6 display mode"
943:
243:based system predating the TRS-80.
24:
609:Matsushita JR series character set
110:; an important example of this is
25:
1311:
1290:Computer graphics data structures
879:. Terminals Working Group (TWG),
758:Freytag (c), Asmus (2020-10-13).
159:
651:and the enhanced version of the
1146:
1116:from the original on 2021-08-21
1097:
1086:from the original on 2021-10-03
1068:
1057:from the original on 2021-10-03
1039:
1003:
890:from the original on 2020-12-24
838:from the original on 2017-07-29
775:Enhanced Teletext specification
1228:"Sharp MZ80K - BASE ZERO game"
1196:, Commodore, 1983, p. 379
1076:"MATRA HACHETTE > ALICE 90"
1011:"Semi-graphics-6 display mode"
804:
785:
766:
751:
733:
440:using a semi-documented trick.
13:
1:
1171:IBM PC XT Technical Reference
726:
598:Mattel Aquarius character set
389:chip designed for their TV's.
1013:. 2021-02-14. Archived from
721:TI calculator character sets
671:Symbols for Legacy Computing
635:Thomson EF9345 character set
260:"DEL" or "rub-out" character
139:Symbols for Legacy Computing
83:mode using a set of special
7:
1280:Computer graphic techniques
1110:La page des fans du VG5000µ
1047:"MATRA HACHETTE > ALICE"
832:"Graphic Tips & Tricks"
664:
48:Color image rendered using
10:
1316:
546:default hardware code page
365:'s default graphics mode (
72:video hardware to emulate
209:used in the Sinclair ZX81
137:, in, for example in the
484:Semigraphical characters
445:Semigraphical characters
385:, which actually used a
327:semigraphical characters
883:. p. 3. L2/19-25.
864:Bettencourt, Rebecca G.
830:Goldklang, Ira (2015).
396:32, Matra Alice 90 and
681:Alpha-mosaic character
620:Sharp MZ character set
542:box-drawing characters
488:box-drawing characters
480:
468:
459:
429:Color Graphics Adapter
379:Acorn Eurocard systems
283:
180:
112:box-drawing characters
81:all points addressable
53:
52:semigraphic characters
41:
1295:Graphics file formats
1174:, IBM, 1983, p. 1-142
800:. Unicode, Inc. 2023.
686:Box-drawing character
474:
465:
452:
334:TRS-80 Color Computer
281:
262:). The assignment in
170:TRS-80 Color Computer
167:
47:
36:Image rendered using
35:
580:gray as seen in the
490:, circles and dots,
475:The keyboard of the
191:matrix of so-called
1246:www.vdsteenoven.com
866:; Bánffy, Ricardo;
629:32 and 90; and the
296:ZX81 character sets
237:polymorphic systems
1033:www.bbcbasic.co.uk
745:www.bbcbasic.co.uk
586:ZX81 character set
582:ZX80 character set
481:
469:
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400:were based on the
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181:
66:character graphics
54:
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1080:old-computers.com
1051:old-computers.com
359:Videotex graphics
195:(square dots) or
16:(Redirected from
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422:attribute bytes
375:Grundy NewBrain
312:Mattel Aquarius
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248:attribute clash
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108:pseudo-graphics
93:mosaic graphics
91:, or sometimes
74:raster graphics
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383:Philips P2000T
377:, many of the
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160:Block graphics
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62:pseudographics
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1170:
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1129:
1118:. Retrieved
1109:
1106:"le VG5000µ"
1099:
1088:. Retrieved
1079:
1070:
1059:. Retrieved
1050:
1041:
1032:
1023:
1015:the original
1005:
991:
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966:
955:. Retrieved
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892:. Retrieved
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840:. Retrieved
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338:Dragon 32/64
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