On MacOS, the option key functions as a modifier key like the shift key. Hold it down and press another key simultaneously. For option - shift, hold down both the option and shift keys and press another key simultaneously.
On Windows, the Alt key functions as a modifier like the shift key. To make special characters, hold down the Alt key and type in the numbers from the numeric keypad.
(Note: I’m mentioning a useful little program because I use it at home on my Macintosh and a Windows machine and it helps you find a special character when you forget the key combination for it. Here’s how the author describes it:
If you don’t want to remember all these numbers, you should try the little shareware utility PopChar from ergonis software. One click, and PopChar displays a table of all characters of the current font. Select the desired character and it instantly appears in your document. You can also insert HTML symbols. PopChar is available for Mac OS 9, Mac OS X, and Windows.)
For posters at the Straight Dope Message Board: You can type in the HTML number code in your post, and after you submit your post the corresponding special character will appear. In an older version of the message board software you could type in the HTML name code, but that doesn’t seem to work with the current version of the board software.
HTML Name Code | HTML Number Code | Glyph | MacOS | Windows | Description |
‘ | ‘ | option - ] | Alt + 0145 | left single quote | |
’ | ’ | option - shift - ] | Alt + 0146 | right single quote | |
‚ | ‚ | single low-9 quote | |||
“ | “ | option - [ | Alt + 0147 | left double quote | |
” | ” | option - shift - [ | Alt + 0148 | right double quote | |
„ | „ | option - shift - w | double low-9 quote | ||
† | † | option - t | Alt + 0134 | dagger | |
‡ | ‡ | option - shift - 7 | Alt + 0135 | double dagger | |
‰ | ‰ | option - shift - r | Alt + 0137 | per mill sign | |
‹ | ‹ | option - shift - 3 | Alt + 0139 | single left-pointing angle quote | |
› | › | option - shift - 4 | Alt + 0155 | single right-pointing angle quote | |
♠ | ♠ | black spade suit | |||
♣ | ♣ | black club suit | |||
♥ | ♥ | black heart suit | |||
♦ | ♦ | black diamond suit | |||
‾ | ‾ | overline, = spacing overscore | |||
← | ← | leftward arrow | |||
↑ | ↑ | upward arrow | |||
→ | → | rightward arrow | |||
↓ | ↓ | downward arrow | |||
™ | ™ | option - 2 | Alt + 0153 | trademark sign | |
" | " | " | double quotation mark | ||
& | & | & | ampersand | ||
< | < | < | less-than sign | ||
> | > | > | greater-than sign | ||
[ | [ | left square bracket | |||
] | ] | right square bracket | |||
– | – | | option - hyphen | Alt + 0150 | en dash |
— | — | | option - shift -hyphen | Alt + 0151 | em dash |
|   | Alt + 0160 | nonbreaking space | ||
¡ | ¡ | ¡ | option - 1 | Alt + 0161 | inverted exclamation |
¢ | ¢ | ¢ | option - 4 | Alt + 0162 | cent sign |
£ | £ | £ | option - 3 | Alt + 0163 | pound sterling |
¤ | ¤ | ¤ | Alt + 0164 | general currency sign | |
¥ | ¥ | ¥ | option - y | Alt + 0165 | yen sign |
¦ or &brkbar; | ¦ | ¦ | Alt + 0166 | broken vertical bar | |
§ | § | § | option - 6 | Alt + 0167 | section sign |
¨ or ¨ | ¨ | ¨ | option - shift - u | Alt + 0168 | umlaut |
© | © | © | option - g | Alt + 0169 | copyright |
ª | ª | ª | option - 9 | Alt + 0170 | feminine ordinal |
« | « | « | option - \ | Alt + 0171 | left angle quote |
¬ | ¬ | ¬ | option - l | Alt + 0172 | not sign |
­ | ­ | | Alt + 0173 | soft hyphen | |
® | ® | ® | option - r | Alt + 0174 | registered trademark |
¯ or &hibar; | ¯ | ¯ | Alt + 0175 | macron accent | |
° | ° | ° | option - shift - 8 | Alt + 0176 | degree sign |
± | ± | ± | option - shift - = | Alt + 0177 | plus or minus |
² | ² | ² | Alt + 0178 | superscript two | |
³ | ³ | ³ | Alt + 0179 | superscript three | |
´ | ´ | ´ | option - shift - e | Alt + 0180 | acute accent |
µ | µ | µ | option - m | Alt + 0181 | micro sign |
¶ | ¶ | ¶ | option - 7 | Alt + 0182 | paragraph sign |
· | · | · | option - shift - 9 | Alt + 0183 | middle dot |
¸ | ¸ | ¸ | option - shift - z | Alt + 0184 | cedilla |
¹ | ¹ | ¹ | Alt + 0185 | superscript one | |
º | º | º | option - 0 | Alt + 0186 | masculine ordinal |
» | » | » | option - shift - \ | Alt + 0187 | right angle quote |
¼ | ¼ | ¼ | Alt + 0188 | one-fourth | |
½ | ½ | ½ | Alt + 0189 | one-half | |
¾ | ¾ | ¾ | Alt + 0190 | three-fourths | |
¿ | ¿ | ¿ | option - shift - ? | Alt + 0191 | inverted question mark |
À | À | À | option - ` A | Alt + 0192 | uppercase A, grave accent |
Á | Á | Á | option - e A | Alt + 0193 | uppercase A, acute accent |
 |  |  | option - i A | Alt + 0194 | uppercase A, circumflex accent |
à | à | à | option - n A | Alt + 0195 | uppercase A, tilde |
Ä | Ä | Ä | option - u A | Alt + 0196 | uppercase A, umlaut |
Å | Å | Å | option - shift - a | Alt + 0197 | uppercase A, ring |
Æ | Æ | Æ | option - shift - ' | Alt + 0198 | uppercase AE |
Ç | Ç | Ç | option - shift - c | Alt + 0199 | uppercase C, cedilla |
È | È | È | option - ` E | Alt + 0200 | uppercase E, grave accent |
É | É | É | option - e E | Alt + 0201 | uppercase E, acute accent |
Ê | Ê | Ê | option - i E | Alt + 0202 | uppercase E, circumflex accent |
Ë | Ë | Ë | option - u E | Alt + 0203 | uppercase E, umlaut |
Ì | Ì | Ì | option - ` I | Alt + 0204 | uppercase I, grave accent |
Í | Í | Í | option - e I | Alt + 0205 | uppercase I, acute accent |
Î | Î | Î | option - i I | Alt + 0206 | uppercase I, circumflex accent |
Ï | Ï | Ï | option - u I | Alt + 0207 | uppercase I, umlaut |
Ð | Ð | Ð | Alt + 0208 | uppercase Eth, Icelandic | |
Ñ | Ñ | Ñ | option - n N | Alt + 0209 | uppercase N, tilde |
Ò | Ò | Ò | option - ` O | Alt + 0210 | uppercase O, grave accent |
Ó | Ó | Ó | option - e O | Alt + 0211 | uppercase O, acute accent |
Ô | Ô | Ô | option - i O | Alt + 0212 | uppercase O, circumflex accent |
Õ | Õ | Õ | option - n O | Alt + 0213 | uppercase O, tilde |
Ö | Ö | Ö | option - u O | Alt + 0214 | uppercase O, umlaut |
× | × | × | Alt + 0215 | multiplication sign | |
Ø | Ø | Ø | option - shift - o | Alt + 0216 | uppercase O, slash |
Ù | Ù | Ù | option - ` U | Alt + 0217 | uppercase U, grave accent |
Ú | Ú | Ú | option - e U | Alt + 0218 | uppercase U, acute accent |
Û | Û | Û | option - i U | Alt + 0219 | uppercase U, circumflex accent |
Ü | Ü | Ü | option - u U | Alt + 0220 | uppercase U, umlaut |
Ý | Ý | Ý | Alt + 0221 | uppercase Y, acute accent | |
Þ | Þ | Þ | Alt + 0222 | uppercase THORN, Icelandic | |
ß | ß | ß | option - s | Alt + 0223 | lowercase sharps, German |
à | à | à | option - ` a | Alt + 0224 | lowercase a, grave accent |
á | á | á | option - e a | Alt + 0225 | lowercase a, acute accent |
â | â | â | option - i a | Alt + 0226 | lowercase a, circumflex accent |
ã | ã | ã | option - n a | Alt + 0227 | lowercase a, tilde |
ä | ä | ä | option - u a | Alt + 0228 | lowercase a, umlaut |
å | å | å | option - a | Alt + 0229 | lowercase a, ring |
æ | æ | æ | option - ' | Alt + 0230 | lowercase ae |
ç | ç | ç | option - c | Alt + 0231 | lowercase c, cedilla |
è | è | è | option - ` e | Alt + 0232 | lowercase e, grave accent |
é | é | é | option - e e | Alt + 0233 | lowercase e, acute accent |
ê | ê | ê | option - i e | Alt + 0234 | lowercase e, circumflex accent |
ë | ë | ë | option - u e | Alt + 0235 | lowercase e, umlaut |
ì | ì | ì | option - ` i | Alt + 0236 | lowercase i, grave accent |
í | í | í | option - e i | Alt + 0237 | lowercase i, acute accent |
î | î | î | option - i i | Alt + 0238 | lowercase i, circumflex accent |
ï | ï | ï | option - u i | Alt + 0239 | lowercase i, umlaut |
ð | ð | ð | Alt + 0240 | lowercase eth, Icelandic | |
ñ | ñ | ñ | option - n n | Alt + 0241 | lowercase n, tilde |
ò | ò | ò | option - ` o | Alt + 0242 | lowercase o, grave accent |
ó | ó | ó | option - e o | Alt + 0243 | lowercase o, acute accent |
ô | ô | ô | option - i o | Alt + 0244 | lowercase o, circumflex accent |
õ | õ | õ | option - n o | Alt + 0245 | lowercase o, tilde |
ö | ö | ö | option - u o | Alt + 0246 | lowercase o, umlaut |
÷ | ÷ | ÷ | Alt + 0247 | division sign | |
ø | ø | ø | option - o | Alt + 0248 | lowercase o, slash |
ù | ù | ù | option - ` u | Alt + 0249 | lowercase u, grave accent |
ú | ú | ú | option - e u | Alt + 0250 | lowercase u, acute accent |
û | û | û | option - i u | Alt + 0251 | lowercase u, circumflex accent |
ü | ü | ü | option - u u | Alt + 0252 | lowercase u, umlaut |
ý | ý | ý | Alt + 0253 | lowercase y, acute accent | |
þ | þ | þ | Alt + 0254 | lowercase thorn, Icelandic | |
ÿ | ÿ | ÿ | option - u y | Alt + 0255 | lowercase y, umlaut |