Code page 437

Code page 437
Code page 437, as rendered by an IBM PC using standard VGA
Alias(es) OEM-US
Language(s) English
Classification Extended ASCII, OEM code page
Extends US-ASCII
Other related encoding(s) Code page 850, CWI-2

Code page 437 is the character set of the original IBM PC (personal computer). It is also known as CP437, OEM-US, OEM 437,[1] PC-8,[2] or 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).

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 in this character set.[nb 1] Many file formats developed at the time of the IBM PC are based on code page 437 as well.

Display adapters

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.

Various Eastern European PCs used different character sets, sometimes user-selectable via jumpers or CMOS setup. These sets were designed to match 437 as much as possible, for instance sharing the code points for many of the line-drawing characters, while still allowing text in a local language to be displayed.

Alt codes

A legacy of code page 437 and other DOS codepages is the set of number combinations used in Windows Alt keycodes.[4][5][6] The user could enter a character by holding down the Alt key and entering the three-digit decimal Alt keycode on the numpad.[4] When Microsoft switched to their proprietary character sets (such as CP1252) and later Unicode in Windows, the original codes were retained (Microsoft added the ability to type a code in the actual character set, such as CP1252, by typing the numpad 0 before the digits[4][7]).

Character set

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

Although the ROM provides a graphic for all 256 different possible 8-bit codes, some APIs will not print some code points, in particular the range 1-31 and the code at 127.[8] Instead they will interpret them as control characters. For instance many methods of outputting text on the original IBM PC would interpret the codes for BEL, BS, CR and LF. Many printers were also unable to print these characters.

Code page 437[9]
_0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _A _B _C _D _E _F
0_ NUL[lower-alpha 1]
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[lower-alpha 1]
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
[lower-alpha 2]
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[lower-alpha 3]
00DF
225
Γ
0393
226
π[lower-alpha 4]
03C0
227
Σ[lower-alpha 5]
03A3
228
σ
03C3
229
µ[lower-alpha 6]
00B5
230
τ
03C4
231
Φ
03A6
232
Θ
0398
233
Ω[lower-alpha 7]
03A9
234
δ[lower-alpha 8]
03B4
235

221E
236
φ[lower-alpha 9]
03C6
237
ε[lower-alpha 10]
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
[lower-alpha 11]
221A
251

207F
252
²
00B2
253

25A0
254
nbsp[lower-alpha 1]
00A0
255

  Letter   Number   Punctuation   Symbol   Other   undefined

Notes

Comparison of characters in the E0 to EF range across various IBM products.

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. 1 2 3 0, 32 (20hex) and 255 (FFhex) 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. 127 (7Fhex) was also sometimes used as Greek capital delta [U+0394, Δ].
  3. 225 (E1hex) is identified by IBM as Latin "Sharp s Small"[10] [U+00DF, ß] but is sometimes rendered in OEM fonts as Greek small beta [U+03B2, β]. The placement of this Latin character among Greek characters suggests intended multi-use.
  4. 227 (E3hex) is identified by IBM as Greek "Pi Small" [U+03C0, π] but is sometimes rendered in OEM fonts as Greek capital pi [U+03A0, Π] or the n-ary product sign [U+220F, ∏].
  5. 228 (E4hex) is identified by IBM as Greek "Sigma Capital" [U+03A3, Σ] but is also used as the n-ary summation sign [U+2211, ∑].
  6. 230 (E6hex) is identified by IBM as Greek "Mu Small" [U+03BC, μ] but is also used as the micro sign [U+00B5, µ]. In Unicode, IBM's Greek GCGID table[11] maps the character in this code page to the Greek letter, but Python, for example, maps it to the micro sign.
  7. 234 (EAhex) is identified by IBM as Greek "Omega Capital" [U+03A9, Ω] but is also used as the ohm sign [U+2126, Ω]. Unicode considers the ohm sign to be equivalent to uppercase omega, and suggests that the latter be used in both contexts.[12]
  8. 235 (EBhex) is identified by IBM as Greek "Delta Small" [U+03B4, δ]. It was also unofficially used for the small eth [U+00F0, ð] and the partial derivative sign [U+2202, ∂]
  9. 237 (EDhex) is identified by IBM as Greek "Phi Small (Closed Form)" [U+03D5, ϕ; or, from the italicized math set, U+1D719, 𝜙] but, in some codecs (e.g. the codec library of Python[13]), is mapped to Unicode as the open (or "loopy") form [U+03C6, φ]. Comparison of IBM's Greek GCGID table[11] with Unicode's Greek code chart[14] shows where IBM, for example, reversed the open and closed forms when mapping to Unicode. This character is also used as the empty set sign [U+2205, ∅], the diameter sign [U+2300, ⌀], and the Latin letter O with stroke [U+00D8, Ø; and U+00F8, ø].
  10. 238 (EEhex) is identified by IBM as Greek "Epsilon Small" [U+03B5, ε] but is sometimes rendered in OEM fonts as the element-of sign [U+2208, ∈]. It was later unofficially used as the euro sign [U+20AC, €]
  11. 251 (FBhex) was also sometimes used as a check mark [U+2713, ✓].

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."

According to an interview with 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.[15]

The selection of graphic characters has some internal logic:

  • Table rows 0 and 1, codes 0 to 31 (00hex to 1Fhex), are assorted dingbats (complementary and decorative characters). The isolated character 127 (7Fhex) also belongs to this group.
  • Table rows 2 to 7 (except character 127, 7Fhex), codes 32 to 126 (20hex to 7Ehex), are the standard ASCII printable characters.
  • Table rows 8 to 10 (8hex to Ahex), codes 128 to 175 (80hex to AFhex), are a selection of international text characters.
  • Table rows 11 to 13 (Bhex to Dhex), codes 176 to 223 (B0hex to DFhex), are box drawing and block characters. This block is arranged so that characters 192 to 223 (C0hex to DFhex) 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,[16] thus filling in gaps in lines and filled areas.
  • Table rows 14 and 15 (Ehex and Fhex), codes 224 to 255 (E0hex to FFhex) are devoted to mathematical symbols, where the first twelve are a selection of Greek letters commonly used in physics. Characters 244 (F4hex) and 245 (F5hex) 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 (B3hex), the vertical line of the box drawing block. Character 244 could also be used as a surrogate for the long s character (ſ). Characters 249 (F9hex) and 250 (FAhex) are almost indistinguishable: the first is slightly larger than the second, which resembles the typographic middle dot (·). The character 255 (FFhex) 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[17] 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.[18]

Internationalization

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

  • Spanish: Á, Í, Ó, and Ú
  • French: À, Â, È, Ê, Ë, Î, Ï, Ô, Œ, œ, Ù, Û, and Ÿ
  • Portuguese: Á, À, Â, Ã, ã, Ê, Í, Ó, Ô, Õ, õ, and Ú
  • Catalan: À, È, Í, Ï, Ò, Ó, and Ú
  • Italian: À, È, Ì, Ò and Ù
  • Icelandic: Á, Ð, ð, Í, Ó, Ú, Ý, ý, Þ and þ
  • Danish/Norwegian: Ø and ø. Character number 237 (EDhex), the small phi (closed form), could be used as a surrogate even though it may not render well (furthermore, it tends to map to Unicode, and/or render in Unicode fonts, as the open-form phi or the closed-vertical-form phi, which are even further from the O with stroke). To compensate, the Danish/Norwegian and Icelandic code pages (865 and 861) replaced cent sign (¢) with ø and the yen sign (¥) 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 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

Notes

  1. 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.

    References

    1. "OEM 437". Go Global Developer Center. Microsoft. Archived from the original on 2016-06-09. Retrieved 2011-09-22.
    2. 1 2 "OEM font". Encyclopedia. PCmag.com. Retrieved 2011-11-15.
    3. Kano, Nadine. "Appendix H Code Pages". Globalization and Localization : Code Page 437 DOS Latin US. Developing International Software. Microsoft. Archived from the original on 2016-03-17. Retrieved 2011-11-14.
    4. 1 2 3 "Glossary of Terms Used on this Site". Microsoft. (Please see the description about the term "Alt+Numpad"). Retrieved 2018-08-17.
    5. Murray Sargent. "Entering Unicode Characters – Murray Sargent: Math in Office". Retrieved 2018-08-17.
    6. "ALT+NUMPAD ASCII Key Combos: The α and Ω of Creating Obscure Passwords". Retrieved 2018-08-17.
    7. "Insert ASCII or Unicode Latin-based symbols and characters - Office Support". Microsoft. Retrieved 2018-08-17.
    8. "SBCS code page information document CPGID 00437". Coded character sets and related resources. IBM. 1986 [1984-05-01]. Archived from the original on 2016-06-09. Retrieved 2011-11-14.
    9. Steele, Shawn (1996-04-24). "cp437_DOSLatinUS to Unicode table" (TXT). 2.00. Unicode Consortium. Archived from the original on 2016-06-09. Retrieved 2011-11-14.
    10. "Code Page (CPGID): 00437". Coded character sets and related resources. IBM. 1984. Retrieved 2017-02-25.
    11. 1 2 "Graphic character identifiers: Alphabetics, Greek". Coded character sets and related resources. IBM. Retrieved 2017-02-25.
    12. The Unicode Consortium (2003-05-21). "Chapter 7: European Alphabetic Scripts". The Unicode Standard 4.0 (PDF). Addison-Wesley (published August 2003). p. 176. ISBN 0-321-18578-1. Retrieved 2016-06-09.
    13. "cpython/cp437.py at master · python/cpython · GitHub". Retrieved 2018-08-17.
    14. "Greek and Coptic: Range: 0370–03FF" (PDF). The Unicode Standard, Version 9.0. Unicode Consortium. Retrieved 2017-02-25.
    15. Edwards, Benj (2015-11-06) [2011]. "Origins of the ASCII Smiley Character: An Email Exchange With Dr. David Bradley". Archived from the original on 2016-11-27. Retrieved 2016-11-27. […] 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 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.
    16. Wilton, Richard (December 1987). Programmer's Guide to PC & PS/2 Video Systems: Maximum Video Performance Form the EGA, VGA, HGC, and MCGA (1st ed.). Microsoft Press. ISBN 1-55615-103-9. ISBN 978-1-55615-103-3.
    17. Mike Jacobs. "MS LineDraw font family - Typography | Microsoft Docs". Microsoft typography. 2.00. Microsoft Corporation. Retrieved 2018-08-17.
    18. Staff (2013-10-26). "WD97: MS LineDraw Font Not Usable in Word". Microsoft. 2.0. Microsoft. KB179422, Q179422. Archived from the original on 2016-03-24. Retrieved 2012-07-01.

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