The ability to transfer information between applications on the same computer, without either application having any foreknowledge of the other, was one of the flagship features of early window-based user interfaces. This means of data transfer remains one of the most useful user-oriented features of the Windows operating system today. Drag and drop is a more recent incarnation of the classic clipboard transfer, allowing users to transfer data between applications by simply dragging between two windows (no clipboard involved). This capability is built on top of Microsoft COM technology, and has become relatively easy to add to most Visual C++ based applications.