Translation:The computer is on the table.
Even though "desk" may be more specifically "书桌“, the term "桌子" can still refer to either "desk" or "table". "The computer is on the desk" should also be accepted.
Especially since computers are usually on desks, and not just on random tables.
Actually weiweiland is correct. I wouldn't have thought it correct, but the term "laptop" only came about to differentiate from the "desk top" computer. Most "desk top" computers are kept on the top of the table that's attached to the drawers of every desk :/
I wrote "The computer is on top of the table." and it didn't accept. "On" and "On top of" are interchangeable in this context, guys.
In Hungarian, they also use postpositions (prepositions that come AFTER the noun they are operating on).
Don't write "The computer is on top of the table" because you'll get marked wrong". Although it means exactly the same thing in English and infers the same in Chinese.
What does this sentence mean without the 上? Like, what would a Chinese speaker envision with 「電腦在桌子。」
Without the 上it is like saying in English "The computer is at the table". The 上 gives the specific position for the computer being "on" the table, rather than, for example, under or beside the table.