This result was already included in our Volume II, but we feel that due to the basic nature of the result, it belongs to this volume. For the sake of the reader of Volume II, where all references to Volume I follow the old numbering, we have included here a table indicating the new number corresponding to each of the old ones.

1 Introduction.- 2 Basic Notions About Models of Computation.- 1.1 Introduction.- 1.2 Alphabets, Words, Sets, and Classes.- 1.3 Inclusion Modulo Finite Variants.- 1.4 Boolean Formulas.- 1.5 Models of Computation: Finite Automata.- 1.6 Models of Computation: Taring Machines.- 1.7 Models of Computation: Nondeterministic Turing Machines.- 1.8 Models of Computation: Oracle Turing Machines.- 1.9 Bibliographical Remarks.- 3 Time and Space Bounded Computations.- 2.1 Introduction.- 2.2 Orders of Magnitude.- 2.3 Running Time and Work Space of Turing Machines.- 2.4 Time and Space Constructibility.- 2.5 Bounding Resources: Basic Definitions and Relationships.- 2.6 Bibliographical Remarks.- 4 Central Complexity Classes.- 3.1 Introduction.- 3.2 Definitions, Properties, and Examples.- 3.3 Computing Functions: Invertibility and Honesty.- 3.4 Polynomial Time Many-one Reducibility.- 3.5 “Natural” NP-complete Sets.- 3.6 “Natural” PSPACE-complete Sets.- 3.7 Padding Arguments.- 3.8 Space Bounded Reducibility.- 3.9 Exercises.- 3.10 Bibliographical Remarks.- 5 Time Bounded Turing Reducibilities.- 4.1 Introduction.- 4.2 Polynomial Time Turing Reducibility: Relativized Classes.- 4.3 Tally and Sparse Sets in NP.- 4.4 Strong Nondeterministic Polynomial Time Reducibility.- 4.5 Self-Reducibility.- 4.6 Exercises.- 4.7 Bibliographical Remarks.- 6 Nonuniform Complexity.- 5.1 Introduction.- 5.2 Classes Defined by Advice Functions.- 5.3 Boolean Circuit Complexity.- 5.4 Turing Machines and Boolean Circuits.- 5.5 Polynomial Advice.- 5.6 Logarithmic Advice.- 5.7 Self-Producible Circuits.- 5.8 A Lower Bound to the Circuit Size of Boolean Functions.- 5.9 Other Nonuniform Complexity Measures.- 5.10 Exercises.- 5.11 Bibliographical Remarks.- 7 Probabilistic Algorithms.- 6.1 Introduction.- 6.2 TheProbabilistic Computational Model.- 6.3 Polynomial Time Probabilistic Classes.- 6.4 Bounded Error Probability.- 6.5 Nonuniform Properties of BPP.- 6.6 Zero Error Probability.- 6.7 Exercises.- 6.8 Bibliographical Remarks.- 8 Uniform Diagonalization.- 7.1 Introduction.- 7.2 Presentability and Other Properties.- 7.3 The Main Theorem.- 7.4 Applications.- 7.5 Exercises.- 7.6 Bibliographical Remarks.- 9 The Polynomial Time Hierarchy.- 8.1 Introduction.- 8.2 Definition and Properties.- 8.3 Characterization and Consequences.- 8.4 Complete Sets and Presentability.- 8.5 BPP and the Polynomial Time Hierarchy.- 8.6 Exercises.- 8.7 Bibliographical Remarks.- References.- Appendix Complementation via Inductive Counting.- Author Index.- Symbol Index.