It will only clash with names that you #include. If you only #include <iostream> and decide to use variables named 'string' (a bad idea since you might decide to use STL strings in the future) then there won't be any problems.
If you do have name conflicts (extremely unlikely in my experience) then you have two choices:
- Rename your variable or function to something else.
- Explicitly specify the namespace that the name belongs to (std:: or whatever:: )
