Code page 437

Code page 437 is the character set of the original IBM PC (personal computer), or MS-DOS. It is also known as CP437, OEM-US, OEM 437,^[1] PC-8,^[2] or MS-DOS Latin US.^[3] The set includes ASCII codes 32–126, extended codes for accented letters (diacritics), some Greek letters, icons, and line-drawing symbols. It is sometimes referred to as the "OEM font" or "high ASCII", or as "extended ASCII"^[2] (one of many mutually incompatible ASCII extensions).

In a strict sense, this character set was not conceived as a code page; it was simply the graphical glyph repertoire available in the original IBM PC. This character set remains the primary font in the core of any EGA and VGA-compatible graphics card. Text shown when a PC reboots, before any other font can be loaded from a storage medium, typically is rendered with this "Code Page".^[4] Many file formats developed at the time of the IBM PC, such as .nfo, define this as the default encoding.

Display adapters

The code page stored in ROM is also called the hardware code page. In Western PCs it typically defaults to code page 437, but various Eastern European PCs used a number of other code pages as their hardware code page, sometimes user-selectable via jumpers or CMOS setup. Arabic and Hebrew PCs and printers even supported multiple software-switchable hardware code pages, also named font pages.

The original IBM PC contained this font as a 9×14 pixels-per-character font stored in the ROM of the IBM Monochrome Display Adapter (MDA) and an 8×8 pixels-per-character font of the Color Graphics Adapter (CGA) cards. The IBM Enhanced Graphics Adapter (EGA) contained an 8×14 pixels-per-character version, and the VGA contained a 9×16 version.

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. All 256 codes were assigned a graphical character in ROM, including the codes from 0 to 31 that were reserved in ASCII for non-graphical control characters.

Alt Codes

A legacy of code page 437 and other DOS codepages is the set of number combinations used in Windows Alt keycodes introduced in the first versions of MS-DOS. The user could enter a character by holding down the Alt key and entering the three-digit decimal Alt keycode on the numpad. When Microsoft switched to more standard character sets (such as CP1252 and later Unicode) in Windows, so many users had memorized the numbers used by their DOS codepage that Microsoft chose to retain the original codes (they added the ability to type a code in the current character set by typing the numpad 0 before the digits).

Characters

The following tables show code page 437. Each character is shown with its equivalent Unicode code point and its decimal code point. See also the notes below as there are multiple equivalent Unicode characters for some code points. The decimal codes are also known as Alt codes.

Although the ROM provides a graphic for all 256 different possible 8-bit codes, some APIs that ostensibly support code page 437 will not print some or all of these code points, in particular the range 1-31 and the code at 127.^[5] Instead they will interpret them as control characters. For instance the BIOS on the original IBM PC has a character-output command that would interpret the codes for CR, LF, BS, and some others. Code 26 (^Z) could not be stored in MSDOS text files as it indicated end of file. Many printers were also unable to print these characters.

Code page 437^[6]

	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F
0_	NUL 0000 0[lower-alpha 1]	☺ 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[lower-alpha 1]	! 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[lower-alpha 2]	Γ 0393 226	π 03C0 227[lower-alpha 3]	Σ 03A3 228[lower-alpha 4]	σ 03C3 229	µ 00B5 230[lower-alpha 5]	τ 03C4 231	Φ 03A6 232	Θ 0398 233	Ω 03A9 234[lower-alpha 6]	δ 03B4 235[lower-alpha 7]	∞ 221E 236	φ 03C6 237[lower-alpha 8]	ε 03B5 238[lower-alpha 9]	∩ 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[lower-alpha 1]
	_0	_1	_2	_3	_4	_5	_6	_7	_8	_9	_A	_B	_C	_D	_E	_F

Notes

When translating to Unicode it should be noted that some codes do not have a unique, single Unicode equivalent; the correct choice may depend upon context.

1. 0, 32 (20_hex) and 255 (FF_hex) all draw a blank space. The use of 255 for U+00A0 Non-breaking space (NBSP) has precedent in word processors designed for the IBM PC.
2. 225 (E1_hex) is both the German sharp S (U+00DF, ß) and the Greek lowercase beta (U+03B2, β).
3. 227 (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, ∏).
4. 228 (E4_hex) is both the n-ary summation sign (U+2211, ∑) and the Greek uppercase sigma (U+03A3, Σ).
5. 230 (E6_hex) is both the micro sign (U+00B5, µ) and the Greek lowercase mu (U+03BC, μ).
6. 234 (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.^[7])
7. 235 (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, ∂).
8. 237 (ED_hex) is supposed to be used as Greek lowercase phi, but is mainly used as the empty set sign (U+2205, ∅) and was also used as the Greek phi symbol in italics (U+03D5, ϕ) to name angles, diameter sign (U+2300, ⌀), and as a surrogate for the Latin lowercase O with stroke (U+00F8, ø).
9. 238 (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, €).

History

The repertoire of code page 437 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 has some internal logic:

• Table rows 0 and 1, codes 0 to 31 (00_hex to 1F_hex), are assorted dingbats (complementary and decorative characters). The isolated character 127 (7F_hex) also belongs to this group.
• Table rows 2 to 7 (except character 127, 7F_hex), codes 32 to 126 (20_hex to 7E_hex), are the standard ASCII printable characters.
• Table rows 8 to 10 (8_hex to A_hex), codes 128 to 175 (80_hex to AF_hex), are a selection of international text characters.
• Table rows 11 to 13 (B_hex to D_hex), codes 176 to 223 (B0_hex to DF_hex), are box drawing and block characters. This block is arranged so that characters 192 to 223 (C0_hex to DF_hex) contain all the right arms and right-filled areas. The original IBM PC MDA display adapter stored the code page 437 character glyphs as bitmaps eight pixels 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,^[8] thus filling in gaps in lines and filled areas.
• Table rows 14 and 15 (E_hex and F_hex), codes 224 to 255 (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 (F4_hex) and 245 (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 (B3_hex), the vertical line of the box drawing block. Character 244 could also be used as a surrogate for the ſ character. Characters 249 (F9_hex) and 250 (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.

Most fonts for Microsoft Windows include the special graphic characters 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 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^[9] 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.^[10]

Internationalization

Code page 437 has a series of international characters, mainly values 128 to 175 (80_hex to AF_hex). However, it lacks several characters important to many Western languages:

• Spanish (Á, Í, Ó, Ú), French (À, Â, È, Ê, Ë, Î, Ï, Ô, Œ, œ, Ù, Û), Portuguese (Á, À, Â, Ã, ã, Ê, Í, Ó, Ô, Õ, õ, Ú), and Catalan (À, È, Í, Ï, Ò, Ó, Ú).
• German sharp S (ß) shares its code point with the beta symbol (β), which is acceptable at the low resolution on the original IBM CGA hardware, but unacceptable at higher resolutions. Most newer glyph sets for code page 437, including those built into the IBM EGA and VGA graphics cards, prefer the German sharp S shape for this character.
• Danish/Norwegian lacks slashed-o 'Ø' and 'ø'. Character number 237 (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 Danish/Norwegian and Icelandic code pages (865 and 861), replaced cent mark (¢) with 'ø' and yen (¥) with 'Ø'.
• Most Greek alphabet symbols were omitted, beyond the basic math symbols. (They were included in the Greek-language code pages 737 and 869.)

Along with the cent (¢), pound sterling (£) and yen/yuan (¥) currency symbols, it has a couple of former 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 code page 850 (DOS Latin-1), code page 852 (DOS Central-European) and code page 737 (DOS Greek), filled the gaps for international use with some compatibility with code page 437 by retaining the single and double box-drawing characters, while discarding the mixed ones (e.g. horizontal double/vertical single). All code page 437 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
• ASCII
• .nfo file format, which uses CP437
• Semi graphical characters
• Atari ST character set, derived from code page 437

References

1. "OEM 437". Go Global Developer Center. Microsoft. Retrieved 22 Sep 2011.
2. "OEM font". Encyclopedia. PCmag.com. Retrieved 15 Nov 2011.
3. "Code Page 437 MS-DOS Latin US". Developing International Software. Microsoft. Retrieved 14 Nov 2011.
4. Systems available in Eastern European, Arabic, and Asian countries often use a different set. The designation "OEM", for "original equipment manufacturer", indicates that the "native" hardware character set supplied in ROM could be changed by the manufacturer to meet different markets.
5. "00437". Code pages by CPGID. IBM. Retrieved 14 Nov 2011.
6. "cp437_DOSLatinUS to Unicode table" (TXT). The Unicode Consortium. Retrieved 14 Nov 2011.
7. The Unicode Consortium, The Unicode Standard 4.0, Chapter 7, "European Alphabetic Scripts", p176. PDF version
8. Richard Wilton, Programmer's Guide to PC & PS/2 Video Systems, 1987, Microsoft Press.
9. Staff (2012). "MS LineDraw - Version 2.00". Microsoft. Microsoft Corporation. Retrieved 1 July 2012.
10. Staff (22 January 2007). WD97 "WD97: MS LineDraw Font Not Usable in Word" Check |url= value (help). Microsoft. Microsoft. Retrieved 1 July 2012.

External links

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