This book contains the thoroughly refereed papers from the 9th International Ershov Informatics Conference, PSI 2014, held in St. Petersburg, Russia, in June 2014.

The 17 revised full papers, 11 revised short papers, and 2 system and experimental papers presented in this book were carefully reviewed and selected from 80 submissions. The volume also contains 5 keynote talks which cover a range of hot topics in computer science and informatics. The papers cover various topics related to the foundations of program and system development and analysis, programming methodology and software engineering and information technologies.