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.

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.

This book constitutes the refereed proceedings of the 20th international Conference on Foundations of Software Technology and Theoretical Computer Science, FST TCS 2000, held in New Delhi, India in December 2000. The 36 revised full papers presented were carefully reviewed and selected from a total of 141 submissions; also included are six invited papers. The volume provides broad coverage of the logical and mathematical foundations of computer science and spans the whole range of theoretical computer science.

This book constitutes the refereed proceedings of the 23rd Conference on Foundations of Software Technology and Theoretical Computer Science, FST TCS 2003, held in Mumbai, India in December 2003. The 23 revised full papers presented together with 4 invited papers and the abstract of an invited paper were carefully reviewed and selected from 160 submissions. A broad variety of current topics from the theory of computing are addressed, ranging from algorithmics and discrete mathematics to logics and programming theory.

This book constitutes the refereed proceedings of the 22nd Conference on Foundations of Software Technology and Theoretical Computer Science, FST TCS 2002, held in Kanpur, India in December 2002. The 26 revised full papers presented together with 5 invited contributions were carefully reviewed and selected from 108 submissions. A broad variety of topics from the theory of computing are addressed, from algorithmics and discrete mathematics as well as from logics and programming theory.

This book constitutes the refereed proceedings of the 20th international Conference on Foundations of Software Technology and Theoretical Computer Science, FST TCS 2000, held in New Delhi, India in December 2000. The 36 revised full papers presented were carefully reviewed and selected from a total of 141 submissions; also included are six invited papers. The volume provides broad coverage of the logical and mathematical foundations of computer science and spans the whole range of theoretical computer science.