This paper suggests that input and output are basic primitives of programming and that parallel composition of communicating sequential processes is a fundamental program structuring method. When combined with a development of Dijkstra's guarded command, these concepts are surprisingly versatile. Their use is illustrated by sample solutions of a variety of a familiar programming exercises.

/pdf/communicating-sequential-processes-2j6tdrg5nx.pdf

Communicating sequential processes

Cryptosystem designers frequently assume that secrets will be manipulated in closed, reliable computing environments. Unfortunately, actual computers and microchips leak information about the operations they process. This paper examines specific methods for analyzing power consumption measurements to find secret keys from tamper resistant devices. We also discuss approaches for building cryptosystems that can operate securely in existing hardware that leaks information.

/pdf/differential-power-analysis-4t7fjmuc7b.pdf

Differential Power Analysis

is one of the most recognizablecharacters in 20th century cinema. HAL is an artiﬁcial agent capable of such advancedlanguage behavior as speaking and understanding English, and at a crucial moment inthe plot, even reading lips. It is now clear that HAL’s creator, Arthur C. Clarke, wasa little optimistic in predicting when an artiﬁcial agent such as HAL would be avail-able. But just how far off was he? What would it take to create at least the language-relatedpartsofHAL?WecallprogramslikeHALthatconversewithhumansinnatural

/pdf/speech-and-language-processing-1xjlmt8snu.pdf

Speech and Language Processing

1 Graphical modeling using L-systems.- 1.1 Rewriting systems.- 1.2 DOL-systems.- 1.3 Turtle interpretation of strings.- 1.4 Synthesis of DOL-systems.- 1.4.1 Edge rewriting.- 1.4.2 Node rewriting.- 1.4.3 Relationship between edge and node rewriting.- 1.5 Modeling in three dimensions.- 1.6 Branching structures.- 1.6.1 Axial trees.- 1.6.2 Tree OL-systems.- 1.6.3 Bracketed OL-systems.- 1.7 Stochastic L-systems.- 1.8 Context-sensitive L-systems.- 1.9 Growth functions.- 1.10 Parametric L-systems.- 1.10.1 Parametric OL-systems.- 1.10.2 Parametric 2L-systems.- 1.10.3 Turtle interpretation of parametric words.- 2 Modeling of trees.- 3 Developmental models of herbaceous plants.- 3.1 Levels of model specification.- 3.1.1 Partial L-systems.- 3.1.2 Control mechanisms in plants.- 3.1.3 Complete models.- 3.2 Branching patterns.- 3.3 Models of inflorescences.- 3.3.1 Monopodial inflorescences.- 3.3.2 Sympodial inflorescences.- 3.3.3 Polypodial inflorescences.- 3.3.4 Modified racemes.- 4 Phyllotaxis.- 4.1 The planar model.- 4.2 The cylindrical model.- 5 Models of plant organs.- 5.1 Predefined surfaces.- 5.2 Developmental surface models.- 5.3 Models of compound leaves.- 6 Animation of plant development.- 6.1 Timed DOL-systems.- 6.2 Selection of growth functions.- 6.2.1 Development of nonbranching filaments.- 6.2.2 Development of branching structures.- 7 Modeling of cellular layers.- 7.1 Map L-systems.- 7.2 Graphical interpretation of maps.- 7.3 Microsorium linguaeforme.- 7.4 Dryopteris thelypteris.- 7.5 Modeling spherical cell layers.- 7.6 Modeling 3D cellular structures.- 8 Fractal properties of plants.- 8.1 Symmetry and self-similarity.- 8.2 Plant models and iterated function systems.- Epilogue.- Appendix A Software environment for plant modeling.- A.1 A virtual laboratory in botany.- A.2 List of laboratory programs.- Appendix B About the figures.- Turtle interpretation of symbols.

/pdf/the-algorithmic-beauty-of-plants-4f9yunhil9.pdf

The Algorithmic Beauty of Plants

Information-hiding techniques have recently become important in a number of application areas. Digital audio, video, and pictures are increasingly furnished with distinguishing but imperceptible marks, which may contain a hidden copyright notice or serial number or even help to prevent unauthorized copying directly. Military communications systems make increasing use of traffic security techniques which, rather than merely concealing the content of a message using encryption, seek to conceal its sender, its receiver, or its very existence. Similar techniques are used in some mobile phone systems and schemes proposed for digital elections. Criminals try to use whatever traffic security properties are provided intentionally or otherwise in the available communications systems, and police forces try to restrict their use. However, many of the techniques proposed in this young and rapidly evolving field can trace their history back to antiquity, and many of them are surprisingly easy to circumvent. In this article, we try to give an overview of the field, of what we know, what works, what does not, and what are the interesting topics for research.

/pdf/information-hiding-a-survey-wve0ipfu9n.pdf

Information hiding-a survey

a survey of the basic coustituents arid fcuturcs of the language is given, and the formal notation, by which the syntactic structure is defined, is esplaincd. The sccnnd chapter lists all the basic symbols, and the syntactic units known as identifiers, numbers and strings are defined. Further, some im.portant notions such as cliiantity and value are defined. The third chapter explains the rules for forming expressions and the meaning of these expressions. Three different types of expressions exist: arithmetic, Boolean (logical) and designational. The fourth chapter describes the operational units of the language, known as statements. The basic statements are : assignment statements (evaluation of a formula), go to statements (explicit break of the sequence of execution of statements), dummy statements, and procedure statements (call for execution of a closed process, defined by a procedure declaration). The formation of more complex structures, having statement character, is explained. These include : conditional statements, for statements, compound statements, and blocks. In the fifth chapter, the units known as declarations, serving for defining permanent properties of the units entering into a process described in the language, are defined. The report ends with two detailed examples of the use of the language and an alphabetic index of definitions.

Revised report on the algorithm language ALGOL 60

After the publication of a preliminary report on the algorithmic language ALGOL,!' 2 as prepared at a conference in Zurich in 1958, much interest in the ALGOL language developed. As a result of an informal meeting held at Mainz in November 1958, about forty interested persons from several European countries held an ALGOL implementation conference in Copenhagen in February 1959. A \"hardware group\" was formed for working cooperatively right down to the level of the paper tape code. This conference also led to the publication by Regnecentralen, Copenhagen, of an ALGOL Bulletin, edited by Peter Naur, which served as a forum for further discussion. During the June 1959 ICIP Conference in Paris several meetings, both formal and informal ones, were held. These meetings revealed some misunderstandings as to the intent of the group which was primarily responsible for the formulation of the language, but at the same time made it clear that there exists a wide appreciation of the effort involved. As a result of the discussions it was decided to hold an international meeting in January 1960 for improving the ALGOL language and preparing a final report. At a European ALGOL Conference in Paris in November 1959 which was attended by about fifty people, seven European representatives were selected-to attend the January 1960 Conference, and they represent the following organizations: Association Francaise de Calcul, British Computer Society, Gesellschaft fur Angewandte Mathematik und . Mechanik, and Nederlands Rekenmachine Genootschap. The seven representatives held a final preparatory meeting at Mainz in December 1959. Meanwhile, in the United States, anyone who wished to suggest changes or corrections to ALGOL was requested to send his comments to the ACM Communications where they were published. These comments then became the basis of consideration for changes in the ALGOL language. Both the SHARE and USE organizations established ALGOL working groups, and both organizations were represented on the ACM Committee on Programming Languages. The ACM Committee met in Washington in November 1959 and considered all comments on ALGOL that had been sent to the ACM Communications. Also, seven representatives were selected to attend the January 1960 international conference. These seven representatives held a final preparatory meeting in Boston in December 1959.

Report on the algorithmic language ALGOL 60

Handbook for Automatic Computation

Absolute and monotonic norms

0.1 On the Etymology of the Word Algorithm.- 0.2 How Algorithms are Characterized.- 0.3 Programming as an Evolutionary Process.- 0.4 How to Solve it.- 1. Routines.- 1.1 The Parameter Concept.- 1.2 Declaration of a Routine.- 1.3 Hierarchical Construction of Routines.- 1.3.1 Primitive Routines and Computational Structures.- 1.3.2 The Principle of Substitution.- 1.3.3 Alternatives.- 1.3.4 Input/Output.- 1.4 Recursive Routines and Systems.- 1.4.1 Examples.- 1.4.2 Proof of Termination.- 1.4.3 Taxonomy of Recursion.- 1.4.4 The Level of Applicative Formulation.- 1.5 Mathematical Semantics: Fixpoint Theory.- 1.5.1 Recursive Routines and Functional Equations.- 1.5.2 Fixpoint Theory.- 1.6 Proofs by Induction of Properties of Routines.- 1.6.1 Computational Induction.- 1.6.2 Structural Induction.- 1.7 Operational Semantics: Machines.- 1.7.1 Unfolding and Folding.- 1.7.2 Partial Computation.- 1.7.3 Text Substitution Machines.- 1.7.4 The Stack Machine.- 1.8 Restriction of the Parameter Domain.- 1.9 Dijkstra's Guards.- 1.10 Pre-Algorithmic Formulations by Means of Choice and Determination.- 1.10.1 The Choice Operator.- 1.10.2 The Determination Operator.- 1.11 Semantics of Non-Deterministic Constructions.- 1.11.1 Pre-Algorithms and Algorithms.- 1.11.2 Deriving Algorithms from Pre-Algorithms.- 1.11.3 Mathematical Semantics of Non-Determinate Routines.- 1.11.4 Operational Semantics of Non-Deterministic Algorithms.- 1.12 Routines with a Multiple Result.- 1.13 Structuring of Routines.- 1.13.1 Structuring by Means of Abstraction and Embedding.- 1.13.2 Segments and Suppressed Parameters.- 1.13.3 Object Declarations.- 1.13.4 Result Parameters and the Actualization Taboo.- 1.14 Routines as Parameters and Results.- 1.14.1 Routines as Results.- 1.14.2 Functional Programming.- 1.14.3 The Delay Rule.- Addendum: Notations.- 2. Objects and Object Structures.- 2.1 Denotations.- 2.2 Scope of a Freely Chosen Designation.- 2.3 Kinds of Objects.- 2.4 Sets of Objects, Modes.- 2.5 Composite Modes and Objects.- 2.6 Selectors, Structures with Direct (Selector) Access.- 2.6.1 Compounds.- 2.6.2 Arrays.- 2.6.3 The Selection Structure of Compound and Array.- 2.7 Mode Variants.- 2.8 Introduction of New Modes: Summary.- 2.9 Recursive Object Structures.- 2.9.1 Definition of Recursive Object Structures.- 2.9.2 Object Diagrams.- 2.9.3 Operational Detailing of Objects.- 2.10 Algorithms with Linear Object Structures.- 2.11 The Recursive Object Structure "File".- 2.11.1 "Knitting" of Sequences.- 2.11.2 Files.- 2.12 Algorithms with Cascade-Type Object Structures.- 2.13 Traversal and Scanning of Recursive Object Structures.- 2.14 Infinite Objects.- 2.14.1 Nexuses of Objects.- 2.14.2 Lazy Evaluation.- 2.15 Some Peculiarities of Arrays.- 2.15.1 Arrays with Computed Index Bounds.- 2.15.2 Induced Operations for Arrays.- 2.16 Routines with Multiple Results Revisited.- Addendum: Notations.- 3. Computational Structures.- 3.1 Concrete Computational Structures.- 3.1.1 Encapsulation Effect.- 3.1.2 Properties of Operations.- 3.1.3 Definition of Concrete Computational Structures.- 3.1.4 Atomic Examples.- 3.2 Abstract Computational Structures and Abstract Types.- 3.2.1 Fundamental Concepts.- 3.2.2 Semantics of Abstract Computational Structures and Abstract Types.- 3.2.3 Completeness of Properties.- 3.2.4 Concretization of an Abstract Type.- 3.2.5 Notation and First Examples.- 3.2.6 Constructors and Selectors.- 3.3 Abstract Arrays.- 3.3.1 One-Side-Flexible Arrays.- 3.3.2 Two-Side-Flexible Arrays.- 3.3.3 Aggregates.- 3.4 Sequence-Type Computational Structures.- 3.4.1 Stack, Deck and Queue.- 3.4.2 Excursus: Divisibility Theory in Semi-Groups.- 3.4.3 Sequence and Word.- 3.4.4 Forgetful Functors.- 3.4.5 Sets.- 3.5 Number-Type Computational Structures.- 3.5.1 Peano Numbers.- 3.5.2 Cycle Numbers and Natural Numbers.- 3.5.3 Excursus: Extension by Means of Formal Quotients.- 3.5.4 Integers.- 3.5.5 Rational Numbers.- 3.5.6 Positional Systems and B-al-Fractions.- 3.6 Changing Abstract Types and Object Structures.- 3.6.1 Type Change and Related Types.- 3.6.2 Concretization.- 3.6.3 Implementation of Concrete Computational Structures.- 3.6.4 Example: Binarization.- 3.6.5 Example: Packing of Objects.- Addendum: Notations.- 4. Transformation into Repetitive Form.- 4.1 Schemes and Transformations.- 4.2 Treatment of Linear Recursion.- 4.2.1 The Technique of Re-Bracketing.- 4.2.2 The Technique of Operand Commutation.- 4.2.3 Function Inversion.- 4.2.4 Function Inversion According to Paterson and Hewitt.- 4.2.5 Function Inversion by Introducing Stacks.- 4.3 Treatment of Non-Linear Recursions.- 4.3.1 Method of Functional Embedding.- 4.3.2 Arithmetization of the Flow of Control.- 4.3.3 Special Cases of Nested Recursion.- 4.3.4 The Technique of Range-of-Values Tabulation.- 4.4 Disentanglement of the Control.- 4.4.1 Disentangled Routines.- 4.4.2 Disentangling Recursive Routines by Means of Function Inversion.- 4.4.3 Reshaping the Type of Control Flow.- 5. Program Variables.- 5.1 The Origin of Program Variables.- 5.1.1 Specialization of the Stack Machine.- 5.1.2 Specialization of the Range-of-Values Machine.- 5.2 Formal Introduction of Program Variables.- 5.2.1 Sequentialization of Object Declarations.- 5.2.2 Program Variables as a Means for Saving Identifiers.- 5.2.3 Expressions with Side-Effects.- 5.2.4 Complete Sequentialization of Collective Assignments.- 5.3 Procedures.- 5.3.1 Program Variables as Parameters.- 5.3.2 Actualization Taboo, Alias Ban and Suppressed Variable Parameters.- 5.3.3 Sharing of Variables.- 5.3.4 Initialization.- 5.3.5 Properties of Program Variables.- 5.4 Axiomatic Description of Programming Languages.- 5.4.1 Predicate Transformers.- 5.4.2 Program Verification.- 5.5 Variables for Structured Objects.- 5.5.1 Selective Alteration.- 5.5.2 Remarks on Input/Output.- Addendum: Notations.- 6. Control Elements.- 6.1 Deparameterization and Formal Treatment of Repetition.- 6.1.1 Deparameterization.- 6.1.2 Semantics of Repetition.- 6.1.3 Analytical Treatment of the Protocol Stack.- 6.2 Jumps.- 6.2.1 Simple Call as a Basic Control Element.- 6.2.2 Introduction of Jumps.- 6.3 The General do-od Construction.- 6.4 Loops.- 6.4.1 Rejecting and Non-Rejecting Repetition.- 6.4.2 Counted Repetition.- 6.5 Loops and Repetitive Systems.- 6.6 Sequential Circuits.- 6.7 Flow Diagrams.- 6.7.1 Classical Flow Diagrams.- 6.7.2 Splitting and Collection.- 6.7.3 Coordinated Flow Diagrams.- 6.8 Petri Nets.- 6.8.1 Theory of Petri Nets.- 6.8.2 Construction of Petri Nets, Connection to Coordinated Flow Diagrams.- 6.9 bool Petri Nets, Signals.- 6.10 nat Petri Nets, Semaphores.- Addendum: Notations.- 7. Organized Storages and Linked Lists.- 7.1 Organized Storages.- 7.1.1 Selective Updating.- 7.1.2 Collecting and Composing Variables.- 7.1.3 Computed Variables.- 7.1.4 Constructing Organized Storages and Generating Variables.- 7.1.5 Advantages and Disadvantages of Organized Storages.- 7.2 Identity of Variables and Alias Ban Revisited.- 7.2.1 Revision of the Assignment Axiom.- 7.2.2 Checking the Actualization Taboo.- 7.3 Implementing Object Structures by Organized Storages.- 7.4 Linked-List Implementation of Organized Storages.- 7.4.1 References to Variables: Pointers.- 7.4.2 Wirth's Connection.- 7.4.3 Link Variables.- 7.4.4 Implementing Computational Structures Using Linked Lists.- 7.4.5 Properties of Pointers.- 7.5 Improvement of Algorithms Working on Linked Lists by Selective Updating.- 7.5.1 Algorithms for One-Way Linked Lists.- 7.5.2 Algorithms for Two-Way Linked Lists.- 7.6 Addressing.- 7.6.1 Addresses for Variables.- 7.6.2 Jump Addresses.- 7.6.3 Genuine Addresses.- 7.6.4 Outlook to Systems Programming.- Addendum: Notations.- Conclusion. Programming as an Evolutionary Process.- Program Specification and Development in a Uniform Language.- Conceptual Organization of the Algorithmic Language.- Tools to Be Used.- Methodology of Programming.

Friedrich L. Bauer

Papers

Revised report on the algorithm language ALGOL 60

Report on the algorithmic language ALGOL 60

Handbook for Automatic Computation

Absolute and monotonic norms

Algorithmic Language and Program Development