Currently I'm learning Japanese by discovering vocabulary and new grammars which I can find in Japanese Windows XP. I have some trouble understanding these grammar elements in the following examples :
ファイルを保存 (Fairu wo hozon)
保存するファイル (Hozon suru fairu)
Google translate says their meanings are "Save the file" and "The file to be saved" respectively. However, I'd like to know which type of grammar are they using. Could you please explain it in detail and give me some similar examples?
保存{ほぞん} is a verbal noun. In other words, it's a noun that you can turn into a verb by adding する.
In your example, however, する has been omitted. To complete the sentence, we can add it back in:
1a. ファイルを 保存する
The combination 保存する can be treated as a single verb meaning "save". It takes a direct object marked with を, in this case ファイル "file".
In your example, する is implied—nouns don't take direct objects, so even though する is omitted, we understand the phrase as though it's there. This is relatively common in certain contexts.
保存するファイル contains a relative clause. We can treat it as derived from the example above:
2a. [ ファイルを 保存する ]
2b. [ ＿＿＿＿＿ 保存する ] ファイル
Here, ファイルを has been pulled out of the clause ("relativized") and turned into a head noun, which is modified by the rest of the phrase. Pulling it out leaves behind a gap, indicated with an underline above.
Note that the direct object marker を disappears when you do this. There's nothing in 2b that tells you ファイル is a direct object. Although the role of ファイル isn't indicated explicitly, the を role is the only one that makes sense, so we can understand the phrase anyway.
We form relative clauses in English all the time. If you aren't familiar with the concept, take a look at the following examples:
3a. [ ボールを 蹴{け}った ]
3b. [ ＿＿＿＿ 蹴った ] ボール4a. [ I kicked the ball ]
4b. the ball [ I kicked _____ ]
Although ボール and the ball appear outside the relative clauses that modify them, it's clear what role they play.