Concepts of Programming Languages Introduction

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Concepts of ProgrammingLanguagesIntroduction

• Högskola I Gävle
• Brahim Hnich
• http//www.csd.uu.se/brahim
• brahim_at_csd.uu.se

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Overview

• Introduction to the course
• goals
• organization
• outline
• Introduction to Concepts of Programming Languages

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Goals

• Increased capacity to express programming
  concepts.
• Improved background for choosing appropriate
  languages.
• Increased ability to learn new languages.
• Understanding the significance of implementation.
  
• Overall advancement of computing.
• Increased ability to design new language.

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Organization

• Course Homepagehttp//www.csd.uu.se/brahim/cpl.
  html
• Schedule
• Lecture slides
• Html version
• postscript version
• Announcements
• Other resources online
• TextbookSebesta, Robert W. "Concepts of
  Programming Languages", Benjamin/Cummings,
  senaste uppl

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Outline

• Introduction
• Functional/Logic Programming Languages
• Describing Syntax and Semantics
• Names, Bindings, Type Checking, and scopes
• Data Types
• Expressions and the assignment Statement
• Statement-Level Control Structures
• Subprograms
• Implementing Subprograms
• Abstract Data Types
• Support for OOP
• Concurrency
• Exception Handling

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Programming Domains I

• Scientific applications
• simple data structures (arrays, matrices)
• control structures (loops and selection)
• large numbers of floating-point arithmetic
• Business applications
• producing elaborate reports
• precise ways of describing and storing decimal
  numbers and character data
• the ability to specify decimal arithmetic
  operations

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Programming Domains II

• Artificial intelligence
• use of symbolic rather than numeric computations
  (linked lists)
• requires more flexibility
• Systems programming
• systems software
• execution time is crucial
• Scripting languages
• putting a list of commands in a file to be
  executed
• Special purpose languages

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Evaluation Criteria I

• Readability the ease with which programs can be
  read and understood the most important criterion
• Overall simplicity
• Too many components is bad
• Multiplicity of features is bad
• operator overloading is sometimes bad
• Orthogonality
• relatively small number of primitive constructs
  can be combined in a relatively small number of
  ways to build the control and data structures of
  the language
• Makes the language easy to learn and read
• Meaning is context independent
• Control statements
• Data types and structures
• Syntax considerations

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Evaluation Criteria II

• Writability is a measure of how easily a
  language can be used to create programs for a
  chosen problem domain.
• Simplicity and orthogonality
• Support for abstraction the ability to define
  and then use complicated structures or operations
  in ways that allow many of the details to be
  ignored.
• Expressivity very powerful operators that allow
  a great deal of computation to be accomplished
  with a very small program.
• Reliability a program is reliable if it performs
  to its specifications under all conditions
• Type checking
• Exception handling
• Aliasing having two or more distinct referencing
  methods, or names for the same memory cell
  (dangerous)
• Readability and writability

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Evaluation criteria III

• Cost
• Programmer training
• Software creation
• Compilation
• Execution
• Compiler cost
• Poor reliability
• Maintenance
• Others
• portability
• generality
• well-definedness

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Primary influences on language design

• Computer architecture
• We use imperative languages, at least in part,
  because we use von Neumann machines
• Programming methodologies
• 1950s and early 1960s
• Simple applications
• worry about machine efficiency
• Late 1960s
• People efficiency became important
• readability, better control structures
• Late 1970s
• Data abstraction
• Middle 1980s
• Object-oriented programming

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Language Categories
Imperative C Pascal Functional Lisp (to
be used in labs) Logic Prolog (to be used in
labs) Object-oriented C Java Object-Pascal
(Delphi)
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Language Design Trade-offs

• Reliability versus cost of execution
• Writability versus readability
• Flexibility versus safety

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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

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Programming Environments
The collection of tools used in software
development UNIX An old operating system and
tool collection Borland C A PC environment for
C and C Smalltalk A language
processor/environment Microsoft Visual C A
large, complex visual environment