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Programming Languages 2nd edition Tucker and Noonan

Programming Languages 2nd edition Tucker and Noonan. Chapter 12 Imperative Programming I really hate this darn machine; I wish they would sell it; It won’t do what I want it to, but only what I tell it. Programmer’s lament (anonymous). Contents. 12.1 What Makes a Language Imperative?

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Programming Languages 2nd edition Tucker and Noonan

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  1. Programming Languages2nd editionTucker and Noonan Chapter 12 Imperative Programming I really hate this darn machine; I wish they would sell it; It won’t do what I want it to, but only what I tell it. Programmer’s lament (anonymous)

  2. Contents 12.1 What Makes a Language Imperative? 12.2 Procedural Abstraction 12.3 Expressions and Assignment 12.4 Library Support for Data Structures 12.5 C 12.6 Ada 12.7 Perl

  3. Imperative Programming • Oldest and most well-developed paradigm • Mirrors computer architecture • Languages • Fortran, Pascal • C, Clite • Ada 83

  4. 12.1 What Makes a Language Imperative? • In a von Neumann machine memory holds: • Instructions • Data • Intellectual heart: assignment statement • Others: • Conditional branching • Unconditional branch (goto)

  5. Flowchart

  6. 12.2 Procedural Abstraction • Proceduralabstraction allows the programmer to be concerned mainly with a function interface, ignoring the details of how it is computed. • The process of stepwise refinement utilizes procedural abstraction to develop an algorithm starting with a general form and ending with an implementation. • Ex: sort(list, len)

  7. 12.3 Expressions and Assignment • Assignment statement is fundamental: • target = expression • Copy semantics: Expression is evaluated to a value, which is copied to the target; used by imperative languages • Reference semantics: Expression is evaluated to an object, whose pointer is copied to the target; used by object-oriented languages.

  8. There exist vast libraries of functions for most imperative languages. • Partially accounts for the longevity of languages like Fortran, Cobol, and C.

  9. Turing Complete • Integer variables, values, operations • Assignment • If • Goto • Re: Structured programming revolution of 1970s replace the goto with while loops.

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