Back in the 1990s I wrote a Shareware word processor for the Commodore Amiga in 68k assembly language named TextEngine. The binary is available to download from Aminet but here is the source code for anyone who wishes to learn from this project.
I used Devpac 2.15 to write TextEngine and the code will of course still compile within Devpac when run under emulation or on a real Amiga.