Perticularly on a forum such as this, one can often find themselves happily typing along, then need something like À, but wait a minute, Most of us are on keyboards that don't have any accented characters. There have been some conventions developed to deal with this, such as using Ae in the above case, or putting an accent mark either before or after the letter it effects (I don't remember which side it's supposed to go on).
This works in a pinch, but makes the text look or read kinda wierd. The best solution is to actually use the characters.
I hear you, you're saying, "But Aaed, I can't enter that character. It's not on my keyboard." Fret not, my Gaelic-typing friends. There is only one environment I've used since studying languages that accepts keyboard input, where I have not find a solution using only the keyboard.
A less than convenient way under Windows and Mac (at least OSX, which is where I saw this), is that both of those platforms provide a seperate application from which you can access the entire character set. you can copy the character into your clipboard and paste it the same as anything else.
My favorite way, is to enter the keycodes directly. A chart comes in handy, but you can easilly tell a keyboard exactly what code you want to use, even if the keyboard does not have that character avaliable. Here is a chart with characters for Gaelic, Spanish, and German, which I culled from a linux man page containing most of the avaliable codes:
lunatic@lugh: ~#cat keycodes.txt
À 300 192 C0 A LATIN CAPITAL LETTER A WITH GRAVE
È 310 200 C8 E LATIN CAPITAL LETTER E WITH GRAVE
Ì 314 204 CC I LATIN CAPITAL LETTER I WITH GRAVE
Ò 322 210 D2 O LATIN CAPITAL LETTER O WITH GRAVE
Ù 331 217 D9 U LATIN CAPITAL LETTER U WITH GRAVE
à 340 224 E0 a LATIN SMALL LETTER A WITH GRAVE
è 350 232 E8 e LATIN SMALL LETTER E WITH GRAVE
ì 354 236 EC i LATIN SMALL LETTER I WITH GRAVE
ò 362 242 F2 o LATIN SMALL LETTER O WITH GRAVE
ù 371 249 F9 u LATIN SMALL LETTER U WITH GRAVE
Á 301 193 C1 A LATIN CAPITAL LETTER A WITH ACUTE
É 311 201 C9 E LATIN CAPITAL LETTER E WITH ACUTE
Í 315 205 CD I LATIN CAPITAL LETTER I WITH ACUTE
Ó 323 211 D3 O LATIN CAPITAL LETTER O WITH ACUTE
Ú 332 218 DA U LATIN CAPITAL LETTER U WITH ACUTE
á 341 225 E1 a LATIN SMALL LETTER A WITH ACUTE
é 351 233 E9 e LATIN SMALL LETTER E WITH ACUTE
í 355 237 ED i LATIN SMALL LETTER I WITH ACUTE
ó 363 243 F3 o LATIN SMALL LETTER O WITH ACUTE
ú 372 250 FA u LATIN SMALL LETTER U WITH ACUTE
ñ 361 241 F1 n LATIN SMALL LETTER N WITH TILDE
Ñ 321 209 D1 N LATIN CAPITAL LETTER N WITH TILDE
¿ 277 191 BF c INVERTED QUESTION MARK
Ä 304 196 C4 A LATIN CAPITAL LETTER A WITH DIAERESIS
Ë 313 203 CB E LATIN CAPITAL LETTER E WITH DIAERESIS
Ï 317 207 CF I LATIN CAPITAL LETTER I WITH DIAERESIS
Ö 326 214 D6 O LATIN CAPITAL LETTER O WITH DIAERESIS
Ü 334 220 DC U LATIN CAPITAL LETTER U WITH DIAERESIS
ä 344 228 E4 a LATIN SMALL LETTER A WITH DIAERESIS
ë 353 235 EB e LATIN SMALL LETTER E WITH DIAERESIS
ï 357 239 EF i LATIN SMALL LETTER I WITH DIAERESIS
ö 366 246 F6 o LATIN SMALL LETTER O WITH DIAERESIS
ü 374 252 FC u LATIN SMALL LETTER U WITH DIAERESIS
ß 337 223 DF B LATIN SMALL LETTER SHARP S
On a PC, to enter these, hold the left ALT key, and on the numeric keypad, enter the second number listed, prefixed with a 0, so that ALT+0224 == à or ALT+0223 == ß
This perticular tactic, I have used under Microsoft Windows, and Linux console (on i386)
The same effect can be achieved on a Mac as well, although there, I believe, you hold the command key and press the letter or something like that.
If all of this fails, (also part of the reason I memorised where I keep keycodes.txt at so well), you can always copy the above chart to a text file an copy from it when needed. So far, this is the only way I have found to enter them in Xwindows, such as how I am typing this post.
I believe that pretty well covers all the ways to do it under these two platforms. I still with the ipod supported them. The Linux manual page from which I culled the above is freely avaliable online. Although I don't have a link to it at the moment, if anyone would like, I can locate and post one. many of the codes are also avaliable via the character maps avaliable in Microsoft Windows and in Mac OSX
Poet and seeker of knowledge