output file

Hi, I need write a couple of strings to a file. The first problem is I don't know the size of strings, maybe long or maybe short. Need I use a buffer to store these strings first? The second problem is there are two parts of strings. I should finish writing one part before writing another part. Need I use two buffers to store these two parts strings?
Thank you very much.

how are the strings being stored that you don't know the size of them? Strings in C are generally (but not always) stored with NULL terminators