She's been using a/the/her computer for two hours.

Dear native English speakers,
I believe that all the sentences below can be used. What's the difference?
(a) She's been using the computer for two hours.
(b) She's been using a computer for two hours.
(c) She's been using her computer for two hours.

Thanks in advance.
Hirashin

(a) Can mean that she's using the only computer there is that is shared among others. It can also have the same meaning as b. (b) The most ambiguous of the three it simply means that she has been using a computer for two hours. It could be her computer or another persons or the only computer or none of those. (c) She is using a computer that belongs to herself.

Also just a quick for your information. The contraction "she's" in these sentences is a combination of "she" and "has" instead of the more common "she" and "is".

Thanks for the help, OoTmaster.

OoTmaster said:

Also just a quick for your information. The contraction "she's" in these sentences is a combination of "she" and "has" instead of the more common "she" and "is".

Click to expand...

Don't worry, OoTmaster. I know that.

All of these sentences are fine. The difference between the first two is the same as the general difference between the usage of "the" and "a".

You probably already understand this (I hope you do!), but, although there are a few minor exceptions, in general, "the" is used when the speaker has an expectation that the audience will understand the specific item being discussed. That is why it is referred to as a "definite article", as opposed to "a", which is an "indefinite article". "A" is used with singular, countable nouns when the speaker does not have an expectation that (or it isn't relevant if) the audience will understand the specific item being discussed.

Thanks for the further explanation, joadbres.