The Image Model

I was reflecting on things that I know now, a couple of decades in to my career, that I wish I had been told at the beginning. Many things came to mind, but the most immediate from a technological perspective was Smalltalk’s image model.

It’s not even the technology of the Smalltalk image that’s relevant, but the model of thinking that works well with it. In Smalltalk, there are two (three) important files for a given machine: the VM is the machine that can run Smalltalk; the image is a snapshot of all of the Smalltalk objects on the machine(; and the sources are the source code for the classes and methods in that image).

This has weird implications for how you work that differ greatly from “compile this text stream” or “interpret this text stream” programming environments. People who have used the ENVY/Developer tool generally seem to wax lyrical and wonder why it was never reinvented, like the rest of software engineering is the beach with the ruins of the Statue of Liberty poking out from the end of the Planet of the Apes. But the bit I wish I had been told about: the image model puts the “personal” in “personal computer” as far as programming is concerned. Every piece of software you write is part of your image: a peer of the rest of the software you wrote, of the software that other people wrote that you added, and of the software that was already there when you first booted the machine.

I wish I had been told to think like that: that each tool or project is not a separate tool or project, but a cumulative addition to the image. To keep everything I wrote, so that the next time I needed something I might not need to write it. To make sure, when using new things, that I could integrate them with the image (it didn’t exist at the time, but TruffleSQUEAK is very much this idea). To give up asking “how can I write software to solve this problem”, and to start asking “how can I solve this problem with software, writing some if necessary”?

It would be the difference between twenty of years of experience and one year of experience, twenty times over.

About Graham

I make it faster and easier for you to create high-quality code.
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