Is 一 in バスルーム and コンピュータ meant to indicate a drawn out vowel? Like ba-su-ruuu-mu and kon-pi-yuuu-ta? Or is it a counter somehow? And it's the line radical (http://www.kanjidamage.com/kanji/1-one-line-radical-%E4%B8%80) right, and not a katakana like the other characters? Other examples include ヨーロッパ and オーストラリア.
Wasn't sure if it was related to this question: Syntactic Properties of "Bare Numerals": 「一」in「其の一」
It's very surprising to me that this hasn't been answered somewhere on the site before, but after quite a bit of searching I can't find anything. This may just be so basic that it has slipped between the cracks.
The ー in these words (and generally in katakana words) represents an extension of the vowel before it. According to Wikipedia, which is actually fairly informative in this case, it's called a 長音符.
The chōonpu is usually used to indicate a long vowel sound in katakana writing, rarely in hiragana writing, and never in romanized Japanese.
That said, I hear it referenced colloquially as 伸ばし棒 almost exclusively (as is mentioned on the Japanese wiki page). I don't actually know a good name for this in English; I would probably just call it a vowel extension.
