btw: Regarding prepositions: When i'm writing "This is a MacBookPro" i'm using "a". But when i would write "This is a(n) MBP", the "M" when read is sounding like an "EM" - would i have to use "an MBP" or "a MBP"? For me it seems more fluent to use "an MBP". Serious question as i'm no native speaker and that bothers me for quite some time now...
Most people don't actually say the letters M B P "em bee pee", even when reading to themselves. They see "a MBP" and they think "a MacBook Pro", which is entirely proper. So "an" is less desirable in my book.
But some initialisms becomes words, like URL. When you're reading it, you might pronounce it "an earl" or "a yew are ell". So either "an URL" or "a URL" is defensible.
To confuse matters further, I'm sure there is no universal agreement on this, especially among native speakers