GEM character set

The GEM character set is the character set of Digital Research's graphical user interface GEM on Intel platforms. It is based on code page 437, the original character set of the IBM PC, and like that set includes ASCII codes 32–126, extended codes for accented letters (diacritics), and other symbols. It differs from code page 437 in using other dingbats at code points 0–31, in exchanging the box-drawing characters 176–223 for international characters and other symbols, and exchanging code point 236 with the symbol for line integral. However, GEM is more similar to code page 865 because the codepoints of Ø and ø match the codepoints in that codepage.

The Motorola-based GEM adaptation for the Atari ST family of computers utilized the similar Atari ST character set. It has swapped ¢ and ø and has also swapped ¥ and Ø (to match code page 437 more). It also has the ß (sharp s) at code point 158, reversed not sign (⌐) at code point 169 (as in code page 437), not sign (¬) at code point 170 (as in code page 437), ½ at code point 171 (as in code page 437), ¼ at code point 172 (as in code page 437), ¨ (diaeresis) at code point 184, ´ (acute) at code point 185, ij at code point 192, IJ at code point 193, Hebrew characters at code points 194-220, section sign (§) at code point 221, logical and at code point 222, infinity sign at code point 223, bullet (•) at codepoint 249, cubed sign (superscript three) at code point 254, the macron at code point 255, ATARI-specific characters at codepoints 5, 6, 7, 14, 15, 28, 29, 30, and 31, LED 0-9 at codepoints 16-25, and ə (Schwa) at codepoint 26. Codepoints 12, 13, and 27 are mapped to the C0 controls.

A slight adaptation for Ventura Publisher is the similar Ventura International character set, it has code points 0-31, 127, and 218-255 empty, and has swapped ¢ and ø and has also swapped ¥ and Ø (to match code page 437 more).

In contrast to this, the GEM-derived file manager ViewMAX, which shipped with some versions of DR DOS as a DOSSHELL replacement, does not use the GEM character set, but loads its display fonts from DOS .CPI files^{[1][2][3][4][5][6]} depending on the system's current code page.

Character set[]

The following table shows the GEM character set. Each character is shown with a potential Unicode equivalent, although some codes do not have a unique, single Unicode equivalent; the correct choice may depend upon context. Note that code point 20 (14₁₆) has an unfilled paragraph sign, and code point 188 (BC₁₆) has a filled paragraph sign.