A reference to a VT100 indicates a VT100 equipped with a Selanar equipped (GR100, or GR100+) VT100. A SG100 equipped VT100 has three modes: the terminal (VT100) mode, the Selanar terminal mode, and the Selanar graphics mode. The routine CTERM is used to switch the terminal between modes. A call to FRAME\ will set the mode to the Selanar terminal mode. Whenever a line is plotted to the screen the mode is changed to Selanar graphics and then back to the Selanar terminal mode. If a program error occurs when the terminal is in the Selanar graphics mode, it is possible that no output will appear. Running the CLEAR command file will reset the device back to terminal mode. The Selanar card does not provide linetypes or XOR capability in the 4010 operation mode.