To start RCA Basic, first load one of the predefined configurations with the menu option below (blue ellipse) following the grey menu:
The Super video option will configure the Elf computer with a Super Video, the Serial option with a serial VT100 terminal and the Pixie option with a CDP 1861.
To start RCA Basic first wait a few seconds (until the data display on the main Elf board shows 14) then press return followed by 'C' for a cold start and 'W' for a warm start.
To run RCA Basic from ElfOs with the possibilty to load and save to disk use the 'ElfOs - BiosIo' menu item. Use the ElfOs command INSTALL to install RCA BASIC and after that use the BASIC4 command to start. This configuration needs an IDE image with ElfOs installed and uses BiosIo, see Installation Elf/Os 2.5 via Biosio.
RCA Basic emulation supports loading program and data files with .rca extension as described in Memory Access