Geoffrey Gordon was the creator of the popular GPSS simulation system language.
[2] He moved to the United States in 1955 where he continued working with digital simulation at Westinghouse Electric Corporation.
At the end of following year (1956) he began working at Bell Labs, writing simulation software for message switching systems.
The project, called the "Sequence Diagram Simulator" was completed at the end of that year.
The use of the program outside of the company was soon recognized by the Cross Industry Marketing Group of IBM.