Comment by lispm

> UI development?

The interface builder was written in Dylan and running inside the Dylan runtime.

The early use of Dylan (actually its precursor language Ralph) was to develop software on a Mac for an external device, like tablets and handheld computers. The development system was an external mainboard attached to a Mac. Apple released eventually a first device with ARM 610 20Mhz CPU, 640Kb RAM and 4MB ROM as a product. A few of the early internal development environments were written in Lisp on the Mac, using a lot of memory (precious and expensive megabytes!).

> Apple Dylan environment

That was a prototype of the Apple Dylan environment, later released as a technical preview. It was also never a product. Apple at that time often developed software prototypes and the released product was then recoded as a more efficient tool. The technical preview was for the Mac and for develop software for the Mac.