This book constitutes the proceedings of the 42nd International Conference on Current Trends in Theory and Practice of Computer Science, SOFSEM 2016, held in Harrachov, Czech Republic, in January 2016. The 43 full papers presented in this volume were carefully reviewed and selected from 116 submissions. They are organized in topical sections named: foundations of computer science; software engineering: methods, tools, applications; and data, information, and knowledge engineering. The volume also contains 7 invited talks in full paper length. .