I agree with Erik that the comments should indicate more of the big picture explaining the authors intentions, rather than an explanation of what an instruction does. Also, my own rule is to attempt to use proper English (insert your native language here) including punctuation and capitalization. I'm not an English major, but I prefer the same kind of language in a comment that this message board tries to enforce.

There are two other points to be made about this example though.

• The first is that since this example is a fairly generic function, the comments by Jan are probably suitable, since there is little more we can infer about the pointers or the function (maybe that's comment enough). If it has more specific characteristics, such as accessing I/O, then that should be explained.
• The second is that when debugging code, especially someone else's, one needs to take the comments with a grain of salt. The code is really the only truth. The comments might explain what the author is doing, or they might be out of synch, especially after many revisions.

GB