Concepts of Programming Languages Chapter 1 Copyright 1998

Why study concepts of PLs? • • • To increase capacity to express programming

Programming Domains • • Scientific applications Business applications Artificial intelligence Systems programming Scripting languages

Language Evaluation Criteria • Readability – Overall simplicity – Too many features is bad

Evaluation Criteria (continued) • Writability – Simplicity and orthogonality – Support for abstraction –

Evaluation criteria (continued) • Cost – Programmer training – Software creation – Compilation –

Primary influences on language design • Computer architecture – We use imperative languages, at

Language Categories • • Imperative (or Procedural) Functional Logic Object-oriented (closely related to Imperative)

Language Design Trade-offs • Reliability versus cost of execution • Writability versus readability •

Implementation Methods • Compilation – Translate high-level program to machine code – Slow translation

Programming Environments • The collection of tools used in software development • UNIX –

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Why study concepts of PLs? • • • To increase capacity to express programming concepts To improve background for choosing appropriate languages To increase ability to learn new languages To better understand the significance of implementation To increase ability to design new languages Overall advancement of computing Copyright © 1998 by Addison Wesley Longman, Inc. 2

Programming Domains • • Scientific applications Business applications Artificial intelligence Systems programming Scripting languages Special purpose languages Others? Copyright © 1998 by Addison Wesley Longman, Inc. 3

Language Evaluation Criteria • Readability – Overall simplicity – Too many features is bad » Multiplicity of features is bad – Orthogonality » Makes the language easy to learn and read » Meaning is context independent – Control statements – Data type and structures – Syntax considerations Copyright © 1998 by Addison Wesley Longman, Inc. 4

Evaluation Criteria (continued) • Writability – Simplicity and orthogonality – Support for abstraction – Expressivity • Reliability – Type checking – Exception handling – Aliasing – Readability and writability Copyright © 1998 by Addison Wesley Longman, Inc. 5

Evaluation criteria (continued) • Cost – Programmer training – Software creation – Compilation – Execution – Compiler cost – Poor reliability – Maintenance • Others – Portability – Generality – Well-definedness Copyright © 1998 by Addison Wesley Longman, Inc. 6

Primary influences on language design • Computer architecture – We use imperative languages, at least in part, because we use von Neumann machines • Programming methodologies – 1950 s and early 1960 s: Simple applications; worry about machine efficiency – Late 1960 s: People efficiency became important; readability, better control structures – Late 1970 s: Data abstraction – Middle 1980 s: Object-oriented programming Copyright © 1998 by Addison Wesley Longman, Inc. 7

Implementation Methods • Compilation – Translate high-level program to machine code – Slow translation – Fast execution • Pure interpretation – No translation – Slow execution – Becoming rare • Hybrid implementation systems – Small translation cost – Medium execution speed Copyright © 1998 by Addison Wesley Longman, Inc. 10

Programming Environments • The collection of tools used in software development • UNIX – An old operating system and tool collection • Microsoft Visual C++ – A large, complex visual environment • Smalltalk – A language processor/environment Copyright © 1998 by Addison Wesley Longman, Inc. 11