Initially, the "SCSI Parallel Interface" (SPI) was the only interface using the SCSI protocol. It features several improvements to the user interface and memory management. Windows 3.0 also featured improvements to the user interface. Quantum also includes refinements to the user interface and interactions. Cutter is the first official graphical user interface (GUI) for radare2. He is also the architect of the modern overlapping windowing graphical user interface (GUI). Intel called their 8251 device a "Programmable Communication Interface". The touchscreen furnishes the remainder of the user interface. The density of the elements on the user interface has decreased. Microsoft began developing a graphical user interface (GUI) in 1981. Significant changes to the user interface were made. Google Wave is extensible through an application programming interface (API). File descriptors form part of the POSIX application programming interface. This is normally done via an application programming interface (API). Windows 2000 introduced the Multilingual User Interface (MUI).