The Early History Of Smalltalk

This is a history written by Alan Kay, who designed early versions of Smalltalk and coined the term "object-oriented."

He starts by describing some early precursors of the ideas that eventually led to object-oriented programming, including Sketchpad and Simula.

Through a series of flukes, I wound up in graduate school at the University of Utah in the Fall of 1966, "knowing nothing." That is to say, I had never heard of ARPA or its projects, or that Utah's main goal in this community was to solve the "hidden line" problem in 3D graphics, until I actually walked into Dave Evans' office looking for a job and a desk. On Dave's desk was a foot-high stack of brown covered documents, one of which he handed to me: "Take this and read it."

Every newcomer got one. The title was "Sketchpad: A man-machine graphical communication system" [Sutherland, 1963]. What it could do was quite remarkable, and completely foreign to any use of a computer I had ever encountered. [...]

Head whirling, I found my desk. On it was a pile of tapes and listings, and a note: "This is the Algol for the 1108. It doesn't work. Please make it work." The latest graduate student gets the latest dirty task.

The documentation was incomprehensible. [...]

Finally, another graduate student and I unrolled the program listing 80 feet down the hall and crawled over it yelling discoveries to each other. The weirdest part was the storage allocator, which did not obey a stack discipline as was usual for Algol. A few days later, that provided the clue. What Simula was allocating were structures very much like the instances of Sketchpad. There were descriptions that acted like masters and they could create instances, each of which was an independent entity. What Sketchpad called masters and instances, Simula called activities and processes. Moreover, Simula was a procedural language for controlling Sketchpad-like objects, thus having considerably more flexibility than constraints (though at some cost in elegance) [Nygaard, 1966, Nygaard, 1983].

This was the big hit, and I've not been the same since.[...]

Five years later, in 1971:

Almost immediately we got into trouble with Xerox when the group decided that the new lab needed a PDP-10 for continuity with the ARPA community. Xerox (which had bought SDS essentially sight unseen a few years before) was horrified at the idea of their main competitor's computer being used in the lab. They balked. The newly formed PARC group had a meeting in which it was decided that it would take about three years to do a good operating system for the XDS SIGMA-7 but that we could build "our own PDP-10" in a year. My reaction was "Holy cow!" In fact, they pulled it it off with considerable panache. MAXC was actually a microcoded emulation of the PDP-10 that used for the first time the new integrated chip memories (1K bits!) instead of core memory. Having practical in house experience with both of these new technologies was critical for the more radical systems to come.