FST TCS 2001

This volume contains the proceedings of the 21st international conference on the Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2001), organized under the auspices of the Indian Association for Research in Computing Science (IARCS). This year's conference attracted 73 submissions from 20 countries. Each s- mission was reviewed by at least three independent referees. In a departure from previous conferences, the ?nal selection of the papers making up the program was done through an electronic discussion spanning two weeks, without a physical meeting of the Program Committee (PC). Since the PC of FSTTCS is distributed across the globe, it is very di?cult to ?x a meeting whose time and venue is convenient for a substantial fraction of the PC. Given this, it was felt that an electronic discussion would enable all members to participate on a more equal footing in the ?nal selection. All reviews, scores, and comments were posted on a secure website, with a mechanism for making updates and automatically sending noti?cations by email to relevant members of the PC. All PC members participated actively in the discussion. The general feedback on the arrangement was very positive, so we hope to continue this in future years. We had ?ve invited speakers this year: Eric Allender, Sanjeev Arora, David Harel, Colin Stirling, and Uri Zwick. We thank them for having readily accepted our invitation to talk at the conference and for providing abstracts (and even full papers) for the proceedings.