Stewart Nelson

Stewart Nelson
Born	The Bronx, New York, United States
Occupation(s)	Mathematician, software developer
Years active	1960s–
Known for	Founding Systems Concepts; early phreaking; contributions to LISP and PDP assembly code

Stewart Nelson is an American mathematician and software developer from The Bronx who played a key role in founding Systems Concepts.

From a young age, Nelson demonstrated a strong aptitude for electronics, inspired by his father, who transitioned from physics to engineering. He completed his education at Poughkeepsie High School in 1963, where he became noted for hacking into international telephone trunk lines and establishing the school's pirate radio station.

In 1963, Nelson began his studies at MIT, where he quickly earned a reputation for linking the AI Lab's PDP-1 and subsequently the PDP-6 to the telephone system, positioning him among the earliest phreakers. During his time at MIT, he also improved hardware by integrating additional instructions directly into the PDP-1 circuitry. On Marvin Minsky's recommendation, Nelson joined Ed Fredkin's Information International Inc. to create PDP-7 software at the MIT Computer Science and Artificial Intelligence Laboratory.

An exceptional programmer, Nelson made significant contributions to the development of LISP, assembly code for Digital Equipment Corporation PDP machines, and other innovations. His efforts played a vital role in advancing early computing and artificial intelligence research.

Famous for his late-night system modifications, Nelson and his associates once rewired MIT's PDP-1 as a practical joke, which affected programs such as the DEC-supplied DECAL assembler utilized by Margaret Hamilton.