Code page 437

Code page 437, as rendered by the IBM PC using a VGA adapter.

IBM PC or MS-DOS code page 437, often abbreviated CP437 and also known as DOS-US, OEM-US or sometimes misleadingly referred to as the OEM font, High ASCII or Extended ASCII,^[1][2] is the character set of the original IBM PC.

In a strict sense, this character set was not born as a code page but was simply the graphical glyph repertoire available in the 9 by 14 pixels-per-character font of the IBM Monochrome Display Adapter (MDA) and the 8 by 8 pixels-per-character font of the Color Graphics Adapter (CGA) cards of the original IBM PC. The ROM of the IBM Enhanced Graphics Adapter (EGA) has an 8 by 14 pixels-per-character version and the VGA adapter expanded the character cell to 9 by 16 for the finer VGA resolution. Today, the character set is still the primary font in the core of any EGA and VGA compatible graphic card; i.e. the text you can see on screen when a PC reboots, before any other font can be loaded from a storage medium, is rendered with this "code page".

All these display adapters have text modes in which each character cell contains an 8-bit character code point (see details), giving 256 possible values for graphic characters. This way, beyond the original ASCII graphical character set (values 32_dec to 126_dec, 95 in total), the implementors put in ROM a handful of miscellaneous characters even for the range 0_dec to 31_dec, reserved in ASCII for control (non graphical) purposes.

The code page has two main uses: as an information interchange code (through files and telecom), in which the values 0_dec to 127_dec plays the same role as in ASCII plus the international text characters 128_dec to 175_dec (see the table below), and as a graphical resource for screen and printers (by merely writing in the video RAM character cell/sending through line the appropriate code), in which the full range can be used to build fine presentations.

Characters

The following is a table representing CP437 using equivalent Unicode characters (see notes below as there are multiple equivalent Unicode characters for some cells).

For many uses, the codes in the range 0_dec to 31_dec and the code 127_dec will not produce these symbols. Some (or all) of them will be interpreted as ASCII control characters. For instance sending the code 13_dec to a terminal or printer is very likely to produce a carriage return and not an eighth-note symbol.

Most fonts for Microsoft Windows include these glyphs at the Unicode indexes shown, as they are part of the WGL4 set that Microsoft encourages font designers to support (the monospaced raster font family Terminal was an early font that replicated all CP437 characters, at least at some resolutions). To draw these glyphs directly from these code values, a Microsoft Windows font called MS Linedraw^[3] replicates all of the CP437 characters, thus providing one way to display DOS text on a contemporary Windows machine as it was shown in DOS, with limitations.^[4]

CP437
	−0	−1	−2	−3	−4	−5	−6	−7	−8	−9	−A	−B	−C	−D	−E	−F
0−	NUL 0000 0	☺ 263A 1	☻ 263B 2	♥ 2665 3	♦ 2666 4	♣ 2663 5	♠ 2660 6	• 2022 7	◘ 25D8 8	○ 25CB 9	◙ 25D9 10	♂ 2642 11	♀ 2640 12	♪ 266A 13	♫ 266B 14	☼ 263C 15
1−	► 25BA 16	◄ 25C4 17	↕ 2195 18	‼ 203C 19	¶ 00B6 20	§ 00A7 21	▬ 25AC 22	↨ 21A8 23	↑ 2191 24	↓ 2193 25	→ 2192 26	← 2190 27	∟ 221F 28	↔ 2194 29	▲ 25B2 30	▼ 25BC 31
2−	SP 0020 32	! 0021 33	" 0022 34	# 0023 35	$ 0024 36	% 0025 37	& 0026 38	' 0027 39	( 0028 40	) 0029 41	* 002A 42	+ 002B 43	, 002C 44	- 002D 45	. 002E 46	/ 002F 47
3−	0 0030 48	1 0031 49	2 0032 50	3 0033 51	4 0034 52	5 0035 53	6 0036 54	7 0037 55	8 0038 56	9 0039 57	: 003A 58	; 003B 59	< 003C 60	= 003D 61	> 003E 62	? 003F 63
4−	@ 0040 64	A 0041 65	B 0042 66	C 0043 67	D 0044 68	E 0045 69	F 0046 70	G 0047 71	H 0048 72	I 0049 73	J 004A 74	K 004B 75	L 004C 76	M 004D 77	N 004E 78	O 004F 79
5−	P 0050 80	Q 0051 81	R 0052 82	S 0053 83	T 0054 84	U 0055 85	V 0056 86	W 0057 87	X 0058 88	Y 0059 89	Z 005A 90	[ 005B 91	\ 005C 92	] 005D 93	^ 005E 94	_ 005F 95
6−	` 0060 96	a 0061 97	b 0062 98	c 0063 99	d 0064 100	e 0065 101	f 0066 102	g 0067 103	h 0068 104	i 0069 105	j 006A 106	k 006B 107	l 006C 108	m 006D 109	n 006E 110	o 006F 111
7−	p 0070 112	q 0071 113	r 0072 114	s 0073 115	t 0074 116	u 0075 117	v 0076 118	w 0077 119	x 0078 120	y 0079 121	z 007A 122	{ 007B 123	| 007C 124	} 007D 125	~ 007E 126	⌂ 2302 127
8−	Ç 00C7 128	ü 00FC 129	é 00E9 130	â 00E2 131	ä 00E4 132	à 00E0 133	å 00E5 134	ç 00E7 135	ê 00EA 136	ë 00EB 137	è 00E8 138	ï 00EF 139	î 00EE 140	ì 00EC 141	Ä 00C4 142	Å 00C5 143
9−	É 00C9 144	æ 00E6 145	Æ 00C6 146	ô 00F4 147	ö 00F6 148	ò 00F2 149	û 00FB 150	ù 00F9 151	ÿ 00FF 152	Ö 00D6 153	Ü 00DC 154	¢ 00A2 155	£ 00A3 156	¥ 00A5 157	₧ 20A7 158	ƒ 0192 159
A−	á 00E1 160	í 00ED 161	ó 00F3 162	ú 00FA 163	ñ 00F1 164	Ñ 00D1 165	ª 00AA 166	º 00BA 167	¿ 00BF 168	⌐ 2310 169	¬ 00AC 170	½ 00BD 171	¼ 00BC 172	¡ 00A1 173	« 00AB 174	» 00BB 175
B−	░ 2591 176	▒ 2592 177	▓ 2593 178	│ 2502 179	┤ 2524 180	╡ 2561 181	╢ 2562 182	╖ 2556 183	╕ 2555 184	╣ 2563 185	║ 2551 186	╗ 2557 187	╝ 255D 188	╜ 255C 189	╛ 255B 190	┐ 2510 191
C−	└ 2514 192	┴ 2534 193	┬ 252C 194	├ 251C 195	─ 2500 196	┼ 253C 197	╞ 255E 198	╟ 255F 199	╚ 255A 200	╔ 2554 201	╩ 2569 202	╦ 2566 203	╠ 2560 204	═ 2550 205	╬ 256C 206	╧ 2567 207
D−	╨ 2568 208	╤ 2564 209	╥ 2565 210	╙ 2559 211	╘ 2558 212	╒ 2552 213	╓ 2553 214	╫ 256B 215	╪ 256A 216	┘ 2518 217	┌ 250C 218	█ 2588 219	▄ 2584 220	▌ 258C 221	▐ 2590 222	▀ 2580 223
E−	α 03B1 224	ß 00DF 225	Γ 0393 226	π 03C0 227	Σ 03A3 228	σ 03C3 229	µ 00B5 230	τ 03C4 231	Φ 03A6 232	Θ 0398 233	Ω 03A9 234	δ 03B4 235	∞ 221E 236	φ 03C6 237	ε 03B5 238	∩ 2229 239
F−	≡ 2261 240	± 00B1 241	≥ 2265 242	≤ 2264 243	⌠ 2320 244	⌡ 2321 245	÷ 00F7 246	≈ 2248 247	° 00B0 248	∙ 2219 249	· 00B7 250	√ 221A 251	ⁿ 207F 252	² 00B2 253	■ 25A0 254	NBSP 00A0 255
	−0	−1	−2	−3	−4	−5	−6	−7	−8	−9	−A	−B	−C	−D	−E	−F

Along with the characters in the range 0_dec to 31_dec (00_hex to 1F_hex), which can be interpreted as ASCII controls as well as graphical dingbats, some characters have overloaded meanings. Implementers of translation to Unicode should note that these codes do not have a unique, single Unicode equivalent and the correct choice depends upon context:

• 0 and 255_dec (FF_hex) both draw a blank space, as does 32_dec (20_hex). The use of 255_dec for U+00A0 Non-breaking space (NBSP) has some precedent in word processors designed for the IBM PC.
• 225_dec (E1_hex) is both the German sharp S (U+00DF, ß) and the Greek lowercase beta (U+03B2, β).
• 227_dec (E3_hex) is the Greek lowercase pi (U+03C0, π), but early fonts such as Terminal use a variant of pi that is ambiguous in case, and therefore can be used for the Greek capital pi (U+03A0, Π) or the n-ary product sign (U+220F, ∏).
• 228_dec (E4_hex) is both the n-ary summation sign (U+2211, ∑) and the Greek uppercase sigma (U+03A3, Σ).
• 230_dec (E6_hex) is both the micro sign (U+00B5, µ) and the Greek lowercase mu (U+03BC, μ).
• 234_dec (EA_hex) is both the ohm sign (U+2126, Ω) and the Greek uppercase omega (U+03A9, Ω). (Unicode considers the ohm sign to be equivalent to uppercase omega, and suggests that the latter be used in both contexts.^[5]).
• 235_dec (EB_hex) is the Greek lowercase delta (U+03B4, δ), but it has also been used as a surrogate for the Icelandic lowercase eth (U+00F0, ð) and the partial derivative sign (U+2202, ∂).
• 237_dec (ED_hex) is supposed to be used as Greek lowercase phi, but is mainly used as the empty set sign (U+2205, $\varnothing$) and was also used as the Greek phi symbol in italics (U+03D5, $\phi\,\!$) to name angles, diameter sign (U+2300, $\varnothing$), and as a surrogate for the Latin lowercase O with stroke (U+00F8, ø).
• 238_dec (EE_hex) is both the Greek lowercase epsilon (U+03B5, ε) and the element-of sign (U+2208, ∈). Later it was often used for the euro sign (U+20AC, €).

Entry on keyboards

In DOS and Windows, most characters from the currently active DOS code page can be inserted by holding down the Alt key and entering the character's three-digit decimal code on the numpad. This technique is called Windows Alt keycodes. One can find out which DOS code page is currently active by issuing the DOS command mode con or chcp.

Difference from ASCII

CP437 is based on ASCII, with the following modifications:

• Codes from the C0 control range (00_hex to 1F_hex) and ASCII DEL (7F_hex) can assume their original function as control characters, but also function as graphic symbols when displayed in text mode from the screen buffer. For example, DEL and most of the C0 control codes are displayed graphically in a screen editor like MS-DOS Editor or when written to the screen via the DOS type command. The graphics include smiling faces, card suits, and musical notes. Code 127_dec (7F_hex), DEL, shows as a "house". This behavior is not specific to CP437, but shared by all DOS code pages and so-called Windows OEM code pages, which generally resemble CP437.
• The high-bit range, 128_dec to 255_dec (80_hex to FF_hex), is mapped to various symbols: a few European characters (accented Latin letters, etc.) in no particular order and not sufficient for representation of most Western European languages; box drawing characters; mathematical symbols; and a few Greek letters commonly used in mathematics and physics.

The repertoire of CP437 was taken from the character set of 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:

"... 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."

The selection of graphic characters, often called bizarre,^{[citation needed]} has some internal logic:

• Table rows 0 and 1, codes 0_dec to 31_dec (00_hex to 1F_hex), are assorted dingbats (complementary and decorative characters). The isolated character 127_dec (7F_hex) also belongs to this group.
• Table rows 2 to 7 (except character 127_dec, 7F_hex), codes 32_dec to 126_dec (20_hex to 7E_hex), are the standard ASCII printable characters.
• Table rows 8_dec to 10_dec (8_hex to A_hex), codes 128_dec to 175_dec (80_hex to AF_hex), are a selection of international text characters.
• Table rows 11_dec to 13_dec (B_hex to D_hex), codes 176_dec to 223_dec (B0_hex to DF_hex), are box drawing and block characters. This block is arranged so that characters 192_dec to 223_dec (C0_hex to DF_hex) of the rows 12_dec and 13_dec (C_hex and D_hex) have all right arms (except 217_dec, D9_hex) or right filled areas (except 221_dec, DD_hex), and this is due to the following technical reason:^[6] the original IBM PC MDA display adapter stored the CP437 character glyphs as bitmaps eight pixels wide, but for visual enhancement displayed them every nine pixels on screen (eight plus an additional gap). Thus characters with connections at their right edge had to duplicate their eighth pixels to avoid visual interruptions in the designs built up with them. This pixel extension is done by special hardware circuitry, and only this character subset is affected.
• Table rows 14_dec and 15_dec (E_hex and F_hex), codes 224_dec to 255_dec (E0_hex to FF_hex) are devoted to mathematical symbols, where the first twelve are a selection of Greek letters commonly used in physics. Characters 244_dec (F4_hex) and 245_dec (F5_hex) are the upper and lower portion of an italic long S, the symbol used as the integral sign (∫), and they can be extended with the character 179_dec (B3_hex), the vertical line of the box drawing block. Characters 249_dec (F9_hex) and 250_dec (FA_hex) are almost indistinguishable: the first is slightly larger than the second, which resembles the typographic middle dot (·). The character 255 (FF_hex) is merely blank, and acts as a kind of non-breaking space in order to arrange math formulae.

Internationalization

CP437 has a series of international characters, mainly values 128_dec to 175_dec (80_hex to AF_hex). However, it lacks many characters important to several Western languages:

• Spanish (Á, Í, Ó, Ú), French (À, Â, È, Ê, Ë, Ì, Î, Ï, Ô, Œ, œ, Ù, Û), and Portuguese (Ã, ã, Õ, õ).
• German sharp S (ß) shares its code point with the beta symbol (β).
• Scandinavian lacks Ø and ø. Character number 237_dec (ED_hex), the empty set symbol, could be used as a surrogate, but its spacing is awkward for display within a word. To compensate, the Norwegian and Danish code pages (CP865 and CP861), replaced cent (¢) with ø, and yen (¥) with Ø.
• Most Greek alphabet symbols. (They were included in the Greek-language code pages CP737 and CP869.)

Along with the cent (¢), pound sterling (£) and yen/yuan (¥) currency symbols, it has a couple of European currency symbols: the florin (ƒ, Netherlands) and the peseta (₧, Spain). The presence of the last is unusual, since the Spanish peseta was never an internationally relevant currency, and also never had a symbol of its own; it was simply abbreviated as "Pt", "Pta", "Pts", or "Ptas". Spanish models of the IBM electric typewriter, however, also had a single position devoted to it.

Later MS-DOS character sets, such as CP850 (DOS Latin-1), CP852 (DOS Central-European) and CP737 (DOS Greek), filled the gaps for international use with some compatibility with CP437 by retaining the single and double box-drawing characters, while discarding the mixed ones (e.g. horizontal double/vertical single). All CP437 characters have similar glyphs in Unicode and in Microsoft's WGL4 character set, and therefore are available in most fonts in Microsoft Windows, and also in the default VGA font of the Linux kernel, and the ISO 10646 fonts for X11.

See also

• Alt codes
• ANSI
• ANSI art
• ASCII
• ASCII art
• Semi graphical characters
• Western Latin character sets (computing)
• Terminal (typeface)

References

1. ^ The Extended ASCII Chart
   Note: CP437 is an extended ASCII code page, but is not the extended ASCII, because numerous incompatible extensions exist.
2. ^ OEM font Definition
3. ^ MS LineDraw - Version 2.00
4. ^ WD97: MS LineDraw Font Not Usable in Word
5. ^ The Unicode Consortium, The Unicode Standard 4.0, Chapter 7, "European Alphabetic Scripts", p176. PDF version
6. ^ Richard Wilton, Programmer's Guide to PC & PS/2 Video Systems, 1987, Microsoft Press.

External links

• Microsoft Code Page 437 reference chart
• IBM Code Page 437 reference chart
• cp437_DOSLatinUS to Unicode table on official Unicode site
• IBM PC memory-mapped video graphics to Unicode on official Unicode site