Editing Code page 437 (section)

== History ==

The repertoire of code page 437 was taken from the character set of [[Wang Laboratories|Wang]] word-processing machines, according to [[Bill Gates]] in an interview with Gates and [[Paul Allen]] that appeared in the 2 October 1995 edition of ''Fortune Magazine:''

<blockquote>
"... We were also fascinated by dedicated word processors from Wang, because we believed that general-purpose machines could do that just as well. That's why, when it came time to design the keyboard for the IBM PC, we put the funny Wang character set into the machine—you know, smiley faces and boxes and triangles and stuff. We were thinking we'd like to do a clone of Wang word-processing software someday."
</blockquote>

According to an interview with [[David Bradley (engineer)|David J. Bradley]] (developer of the PC's [[ROM-BIOS]]) the characters were decided upon during a four-hour meeting on a plane trip from Seattle to Atlanta by Andy Saenz (responsible for the video card), Lew Eggebrecht (chief engineer for the PC) and himself.<ref name="Edwards_2015">{{cite web |title=Origins of the ASCII Smiley Character: An Email Exchange With Dr. David Bradley |author-first=Benj |author-last=Edwards |date=2015-11-06 |orig-year=2011 |url=http://www.vintagecomputing.com/index.php/archives/790/the-ibm-smiley-character-turns-30#more-790 |access-date=2016-11-27 |url-status=live |archive-url=https://web.archive.org/web/20161128185613/http://www.vintagecomputing.com/index.php/archives/790/the-ibm-smiley-character-turns-30 |archive-date=2016-11-28 |quote=If you look at the first 32 characters in the [[IBM PC]] character set you'll see lots of whimsical characters — smiley face, musical notes, playing card suits and others. These were intended for character based games [...] Since we were using 8-bit characters we had 128 new spots to fill. We put serious characters there — three columns of foreign characters, based on our [[Datamaster (IBM)|Datamaster]] experience. Three columns of block graphic characters [...] many customers with Monochrome Display Adapter would have no graphics at all. [...] two columns had math symbols, greek letters (for math) and others [...] about the first 32 characters (x00-x1F)? [...] These characters originated with teletype transmission. But we could display them on the character based screens. So we added a set of "not serious" characters. They were intended as display only characters, not for transmission or storage. Their most probable use would be in character based games. [...] As in most things for the IBM PC, the one year development schedule left little time for contemplation and revision. [...] the character set was developed in a three person 4-hour meeting, and I was one of those on that plane from Seattle to Atlanta. There was some minor revision after that meeting, but there were many other things to design/fix/decide so that was about it. [...] the other participants in that plane trip were Andy Saenz — responsible for the video card, and Lew Eggebrecht — the chief engineer for the PC.}}</ref>

The selection of graphic characters has some internal logic:
* Table rows 0 and 1, codes 0 to 31 (00<sub>hex</sub> to 1F<sub>hex</sub>), are assorted [[dingbat]]s (complementary and decorative characters). The isolated character 127 (7F<sub>hex</sub>) also belongs to this group.
* Table rows 2 to 7, codes 32 to 126 (20<sub>hex</sub> to 7E<sub>hex</sub>), are the standard [[ASCII]] printable characters.
* Table rows 8 to 10, codes 128 to 175 (80<sub>hex</sub> to AF<sub>hex</sub>), are a selection of international text characters.
* Table rows 11 to 13, codes 176 to 223 (B0<sub>hex</sub> to DF<sub>hex</sub>), are [[box-drawing character|box drawing]] and [[Unicode symbols|block]] characters. This block is arranged so that characters 192 to 223 (C0<sub>hex</sub> to DF<sub>hex</sub>) contain all the right arms and right-filled areas. The original [[IBM PC]] [[IBM Monochrome Display Adapter|MDA]] display adapter stored the code page 437 character [[glyph]]s as [[bitmap]]s eight [[pixel]]s wide, but for visual enhancement displayed them every nine pixels on screen. This range of characters had the eighth pixel column duplicated by special hardware circuitry,<ref name="Wilton_1987"/> thus filling in gaps in lines and filled areas. The VGA adapter allows this behaviour to be turned on or off.<ref>Joshua D. Neal, [http://osdever.net/FreeVGA/vga/attrreg.htm#10 Attribute Controller Registers: Attribute Mode Control Register], Hardware Level VGA and SVGA Video Programming Information Page: bit 2 is Line Graphics Enable.</ref>
* Table rows 14 and 15, codes 224 to 254 (E0<sub>hex</sub> to FE<sub>hex</sub>) are devoted to mathematical symbols, where the first twelve are a selection of Greek letters commonly used in physics.

Most fonts for [[Microsoft Windows]] include the special graphic characters at the Unicode indexes shown, as they are part of the [[Windows Glyph List 4|WGL4]] set that Microsoft encourages font designers to support. (The monospaced raster font family [[Terminal (typeface)|Terminal]] was an early font that replicated all code page 437 characters, at least at some resolutions.) To draw these characters directly from these code points, a [[Microsoft Windows]] font called MS Linedraw<ref name="LineDraw"/> replicates all of the code page 437 characters, thus providing one way to display DOS text on a modern Windows machine as it was shown in DOS, with limitations.<ref name="WD97"/>

'''Code page 1055''', also known as HP symbol set 0L,<ref>{{cite web|title=HP Symbol sets|url=https://www.pclviewer.com/resources/pcl_symbolset.html}}</ref> is a subset which includes the box-drawing, half-blocks, black circles (the black circle replaces the bullet, which replaces the middle dot in this code page), and black square, and moves them to the upper half; the space is also included.<ref>{{cite web|title=Code Page 1055|url=https://www-03.ibm.com/systems/resources/systems_i_software_globalization_pdf_cp01055z.pdf|archive-url=https://web.archive.org/web/20130121110539/http://www-03.ibm.com/systems/resources/systems_i_software_globalization_pdf_cp01055z.pdf|archive-date=2013-01-21}}</ref>