Not sure who invented dumping and loading images, but the first Lisp did that already around 1960. From there it spread to Smalltalk in the 70s. A typical MIT

Not sure who invented dumping and loading images, but the first Lisp did that already around 1960. From there it spread to Smalltalk in the 70s. A typical MIT Lisp Machine OS in the 80s recorded for all functions/etc. where they were defined and one edits a function by calling (ed 'foo) (or by pressing M-. in the editor on a function name) and then the source file with the function gets edited. So the Lisp IDE knows that foo is defined in the file hans:graphics;editor;foo.lisp.273 (where 273 is the version number or the file). If one saved an image, this information is stored and restored on starting the image. Common Lisp systems today still record the source location, but they lack the versioned file system and they also usually not record a particular location from a source code version system like SVN or GIT. What Xerox Smalltalk did (and something similar did Xerox Interlisp-D) was to manage source code in a distribution file and a changes file. Thus where the MIT Lisp Machine IDE tracks a multitude of versioned files (and the user has to somewhat manage them by creating them, registering them, compiling, loading them), the Xerox Smalltalk abstracts the editing away from files and manages the source storage in a file mostly invisible for the user. Thus a Smalltalk class browser does not display files, but it displays individual definitions. Since the compiled code is some high-level byte-code, source code can also in a more limited way computed from the compiled code. Similar: Xerox Interlisp-D (which was a Lisp IDE, which ran on the same hardware as the Smalltalk machines from Xerox), which also managed source code (using tools like the File Package and Masterscope), but the source code is actually Lisp data and the main code editor is a structure editor - not a text editor. Xerox called it a residential system - since the source is actually data in the image and the File Package manages to track the changes and keep external versions of the source. I have actually no idea which ML also a) works with images and b) manages source code. Would be interesting to hear more about that.