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 # LISP and beyond from bare metal
 
 It's `eval`s all the way up
+
+## Background
+
+In 2022 I wrote a LISP interpreter in PDP-11 assembly,
+hand-translated it into machine code,
+and toggled it in directly to the front panel
+of my PhD advisor's PiDP-11.
+I kept as close as possible
+to the system described in John McCarthy's original paper
+(other than fixing the known bug in `eval`).
+
+This is that project.
+The original plan involved using it
+to bootstrap an even better interpreter,
+but I lost some momentum
+when I realized
+the thing I created had dynamic instead of lexical scoping,
+and also when
+the PiDP-11 got turned off
+and lost its emulated memory contents.
+
+I gave a little presentation on it anyway;
+the slides for that can be found
+[here](https://jacquescomeaux.xyz/lisp-from-scratch.pdf).
+In short, S-Functions manipulate S-Expressions,
+but descriptions of S-Functions *are* S-Expressions.
+`eval` is the S-Function that reads an S-Expression
+which describes an S-Function,
+and does the thing that that description describes.
+
+## Learning more
+
+If you want to know more
+and know how to find me in real life,
+please do so
+and I'd be happy to talk
+about any of this stuff in more detail.