Code page 437

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

IBM PC or MS-DOS code page 437, often abbreviated CP437 and also known asDOS-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 theIBM 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 theIBM 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 EGAand 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 a 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 to 126, 95 in total), the implementors put in ROM a handful of miscellaneous characters even for the range 0 to 31, reserved in ASCII for control (non graphical) purposes.

So this code page has two main uses: as an information interchange code (through files and telecom), in which the values 0 to 127 plays the same role as in ASCII plus the international text characters 128 to 175 (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 the equivalent Unicode characters. Standard ASCII and ISO 8859-1 (Latin-1) character glyphs, along with the Greek letters, are shown as coloured cells.

Due to the dual use of values in the range 0 to 31 (hexadecimal 00 to 1F), there are two sets for these, the first being their meanings as ASCII control characters and the second their graphical output on screen/printer.

For value 127 (7F), its graphical output is shown in the last table, its meaning being the ASCII control character "DEL" (delete), Unicode value U+007F. A Microsoft Windows font called MS Linedraw ^[3] replicates all of the CP437 characters, being one way to display an old DOS text on a contemporary Windows machine in the same way as it was written with DOS. Another more common font, called Terminal, also replicates all CP437 characters (but is not a vector font).

CP437 head
	—0	—1	—2	—3	—4	—5	—6	—7	—8	—9	—A	—B	—C	—D	—E	—F
0−	NUL 0000 0	SOH 0001 1	STX 0002 2	ETX 0003 3	EOT 0004 4	ENQ 0005 5	ACK 0006 6	BEL 0007 7	BS 0008 8	HT 0009 9	LF 000A 10	VT 000B 11	FF 000C 12	CR 000D 13	SO 000E 14	SI 000F 15
1−	DLE 0010 16	DC1 0011 17	DC2 0012 18	DC3 0013 19	DC4 0014 20	NAK 0015 21	SYN 0016 22	ETB 0017 23	CAN 0018 24	EM 0019 25	SUB 001A 26	ESC 001B 27	FS 001C 28	GS 001D 29	RS 001E 30	US 001F 31
	—0	—1	—2	—3	—4	—5	—6	—7	—8	—9	—A	—B	—C	—D	—E	—F

CP437
	—0	—1	—2	—3	—4	—5	—6	—7	—8	—9	—A	—B	—C	—D	—E	—F
0−	FSP 2007 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

Legend: yellow cells are control characters, blue cells are punctuation, purple cells are numbers, green cells are ASCII letters, and pink cells are international letters.

NOTE: graphical output for characters 0 (00), 32 (20), and 255 (FF) are mere blank cells, without printable marks of any kind.

NOTE: the graphical output chosen for character number 0 (00) is U+2007 FIGURE SPACE (FSP), a space of the same width as digits in the variable-pitch fonts.

Below is a sample of text in the Terminal font, which is based on code page 437. If you don't have this font installed, the text will be displayed in the default monospaced font.

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

[edit]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.

[edit]Difference from ASCII

CP437 is based on ASCII, with the following modifications:

• Codes from the C0 control range (hex 00 to 1F) and ASCII DEL (7F) 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 (7F), 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 to 255 (80 to FF), 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, has some internal logic:

• Table rows 0 and 1, codes 0 to 31 (00 to 1F), are assorted dingbats (complementary and decorative characters). The isolated character 127 (7F) also belongs to this group.
• Table rows 2 to 7 (except character 127, 7F), codes 32 to 126 (20 to 7E), are the standard ASCII printable characters.
• Table rows 8 to 10 (8 to A), codes 128 to 175 (80 to AF), are a selection of international text characters.
• Table rows 11 to 13 (B to D), codes 176 to 223 (B0 to DF), are box drawing and block characters. This block is arranged so that characters 192 to 223 (C0 to DF) of the rows 12 and 13 (C and D) have all right arms (except 217, D9) or right filled areas (except 221, DD), and this is due to the following technical reason:^[4] the original IBM PC MDA display adapter stored the CP437 character glyphs asbitmaps 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 and 15 (E and F), codes 224 to 255 (E0 to FF) are devoted to mathematical symbols, where the first twelve are a selection of Greek letters commonly used in physics. Characters 244 (F4) and 245 (F5) 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), the vertical line of the box drawing block. Characters 249 (F9) and 250 (FA) are almost indistinguishable: the first is slightly larger than the second, which resembles the typographic middle dot (·). The character 255 (FF) is merely blank, and acts as a kind of non-breaking space in order to arrange math formulae.

[edit]Internationalization

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

• It lacks many characters for 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).
• It has umlauts for German (Ä, ä, Ö, ö, Ü, ü), although sharp S (ß) shares its code point with the beta symbol (β).
• It has Scandinavian Æ, æ, Å, å, Ä, ä, Ö, ö but lacks Ø and ø. Character number 237, 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 edition replaced cent (¢) with ø, and yen (¥) with Ø.

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 a surprise, 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 theIBM 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 more or less similar glyphs in Unicode and in Microsoft's WGL4character set, and therefore are available in most fonts in Microsoft Windows, and also in the default VGA font of the Linux kernel, and theISO 10646 fonts for X11.

[edit]Multiple-meaning character glyphs

Along with the characters in the range 0 to 31 (hex 00 to 1F), which can be interpreted as ASCII controls as well as graphical dingbats, some characters have overloaded meanings, depending upon context:

• 225 (E1) is both the German sharp S (U+00DF, ß) and the Greek lowercase beta (U+03B2, β).
• 227 (E3) 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 (E4) is both the n-ary summation sign (U+2211, ∑) and the Greek uppercase sigma (U+03A3, Σ).
• 230 (E6) is both the micro sign (U+00B5, µ) and the Greek lowercase mu (U+03BC, μ).
• 234 (EA) 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 (EB) 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 (ED) is supposed to 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, ) to name angles, diameter sign (U+2300, ), and as a surrogate for the Latin lowercase O with stroke (U+00F8, ø).
• 238 (EE) is both the Greek lowercase epsilon (U+03B5, ε) and the element-of sign (U+2208, ∈). Also, in some dot matrix ticket printers (with CP437 in ROM), it is used today for the euro sign (U+20AC, €) in European countries where the euro is the official currency.

Fixed control values−	NUL 0000 0	DEL 007F 127	Alternate character values−	β 03B2 225	2205 237	∈ 2208 238

The Unicode character U+03D5 GREEK PHI SYMBOL () would be a better choice^[6] for value number 237 (ED) of CP437.

The main reason for these ambiguities is that the CP437 character set of the original IBM PC MDA and CGA display adapters, as well as that of compatible printers, was fixed in ROM and could not be changed by software, so developers and users tried to take the maximum advantage of the available resources.

Implementors of mapping tables to Unicode should note that these "unified" characters may not have a unique, single meaning: the correct choice depends upon context.

sumber : wikipedia