WIMP and task swapping system by Steve Taylor written in 1993 requiring MasterDOS but also compatible with MasterBASIC.
Driver (stylised as DRiVER with a steering wheel icon as the dot of the 'i') is a mostly single-tasking enviroment with the capability to swap up to 12 loaded programs via the Driver Desktop's memory management features.
Some elements of multi-tasking can be introduced with specially written applications (such as the Clock on DRiVER Extras) but this is not available natively.
The primary application is the File Manager which at starting is the only program loaded (it can be set to auto-run in the preferences along with opening the drive contents) to give access to programs and settings in a similar way to the 'Program Manager' in early Microsoft Windows versions - it even uses the same expression when quitting with 'This will end your Driver session'.
Applications can be written to use Driver and utilise a bootstrap file type to load code or BASIC files, MasterDOS RAMdisks and directories are supported.
Driver allows exiting to BASIC and adds a new command 'DRIVER' to return to the environment and applications but the BASIC session will be closed.
Driver has a clipboard system that allows data to be cut and pasted either inside or between applications.
Technical details of Driver and application construction were in Search: “Machine Code Made Easy - Part 23” through to Machine Code Made Easy - Part 28.
Some improvements and additional applications (including Alarm Clock, Calendar, Art Grabber, Paintbrush, Cardfile) and other bits and pieces came out on the Driver Extras disk.