Flexemu is a classic Computer emulation based on the Motorola MC6809.

This processor together with a whole set of peripherals like floppy
disk controller (WD1793), parallel interface (MC6821), serial interface
(MC6850), real time clock (MC146818) and video interface emulates a
Microcomputer EurocomII/V5 or EurocomII/V7 which was developed by
Eltec Elektronik in Mainz/Germany at about 1980.

The operating system running on it is called FLEX. It was developed by
Technical Systems Consultants (TSC) at about 1979. It fits into 8KByte
memory. Its "Disk Operating System" consists of 27 System calls and the
"File Management System" of 3 system calls. The processor itself can
address 64 KByte of memory.

Several (cross) assemblers, debugger, compilers, textprocessing systems,
and even a circuit board layout system and a videotext editing system
are available. And last but not least several arcade-like games.

Flexemu comes with the original FLEX documentation as available from
the FLEX User Group.