ACM-SIAM Algorithmic Principles of Computer Systems (APoCS20), January 8, 2020, Hilton Salt Lake City Center, Salt Lake City, Utah, USA. Colocated with SODA, SOSA, and Alenex. Contributed papers are sought in all areas of algorithms and architectures that offer insight into the performance and design of computer systems. Topics of interest include, but are not limited to algorithms and data structures for: databases, compilers, emerging architectures, energy efficient computing, high-performance computing, management of massive data, networks, including mobile, ad-hoc and sensor networks, operating systems, parallel and distributed systems, and storage systems.