15.3.3 Unix/Windows User Interface Library
Some programs' main interaction with the operating system is drawing on the screen. It is often possible to write such programs using a cross platform user interface library.
A cross-platform user interface library is a library providing basic windowing functions which has been implemented separately for Unix and Windows. The program calls generic routines which are translated into the appropriate calls on each platform. These libraries generally provide a good look and feel on each platform, so this can be a reasonable approach for programs which do not require additional services from the system.
The main disadvantage is the least common denominator effect: the libraries often only provide functionality which is available on both Unix and Windows. Features specific to either Unix or Windows may be very useful for the program, but they may not be available via the library.