Object Windows

All windows under OS/2's Presentation Manager are objects. The windows that people are familiar with all manifest themselves on the screen — scroll bars, child windows, etc. Object windows, on the other hand, do not have this visual property. Since they do not display anything on the screen, they don't have to handle many of the events like WM_PAINT, WM_CHAR, etc. They are free to do whatever a programmer intends them to do, including carrying out a lengthy task and receiving messages at the same time. A programmer defines all messages going to an object window and all messages that an object window sends. An object window communicates with other windows by posting of these messages.