XCON was the expert system that configured computer hardware for Digital Equipment Corporation in the 1980s.
XCON was originally called R1 and was developed at Carnegie Mellon University for Digital Equipment Corporation, often abbreviated DEC. Its purpose was to help configure VAX computer systems by selecting compatible components and producing appropriate system layouts and documentation.
The system used production rules to apply configuration knowledge. This was a practical industrial problem: a VAX order could contain many hardware components, and incompatibilities or omissions could be costly. XCON helped automate part of the process and became one of the best-known examples of a commercially useful expert system.
The names R1 and XCON can cause confusion. R1 was the original name, while XCON became the later and more familiar name. The system is also distinct from MYCIN, which was a Stanford medical expert system rather than a hardware-configuration tool.