The Commodore 128 Developer's Package is a full featured 6502 development environment which runs on the C128.

The package consists of a full screen editor, a powerful assembler and a collection of tools and utility routines that support C64 fast loading 1571/81 burst loading, RAM expansion access, mouse usage and more. The editor and assembler were developed by Fred Bowen and Hedley Davis of Commodore Engineering as an alternative to VAX 6502 development tools.