With only 28 instructions, the PDP-1 computer was very simple but also highly flexible and modular, allowing for many different and surprisingly-powerful applications. Its early users were sophisticated technically so the PDP-1 quickly expanded into application areas even its inventors had not foreseen.

This section explores some of the significant ways in which the PDP-1 was used and covers timesharing, process control, scientific research, the game Spacewar!, graphics & music, and, finally, the start of the Digital Equipment Corporation’s user group known as DECUS.