OPERATING SYSTEMS AND LANGUAGE TRANSLATORS

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OPERATING SYSTEMS AND LANGUAGE TRANSLATORS

• CIS 2380
• TERM 2 LANGUAGE TRANSLATORS
• Lee McCluskey lee_at_hud.ac.uk
• TERM 1 OPERATING SYSTEMS
• Roger England r.england_at_hud.ac.uk

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TERM 2 resources

• http//scom.hud.ac.uk/scomtlm/cas380/
• There will be a link from Blackboard..

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TERM 1 format

• 1 Lecture 1 Tutorial or Practical
• A mix of practical theory.

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Assessment

• Exam (70) examining BOTH terms but concentrating
  on term 2.

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Language Translators

• Computer Systems are full of FORMAL LANGUAGES
  HTML, XML, Java, Pascal, BNF, Z, VDM, Python,
  Lingo, C
• There are languages for programming, for data,
  for database manipulation, for mark-up, for
  specification ..
• Sentences (programs) of LANGUAGES have to be
  compiled/interpreted/translated/executed/analysed
• by programs

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Compilers

• Are the most commonly known language translator
• A COMPILER translates a program P written in a
  HIGH LEVEL language into a program Q written in
  a LOW LEVEL language eg Java -gt Byte code
• Question what is the relationship between
  programs P and Q ??????????

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Interpreters

• Are commonly known language translators
• What is the difference between Interpreters and
  Compilers?

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Interpreters

• Are commonly known language translators
• What is the difference between Interpreters and
  Compilers?
• ANSWER Interpreters analyse a program written in
  a HIGH LEVEL language AND execute it. Eg
  languages such as Prolog, Scheme, Haskell, Basic
  have interpreters
• Compilers analyse then translate,
• Interpreters analyse then execute.
• Interpreted code execution is invariably slower
  than compiled code execution..

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Some Jargon

• Syntax the marks or symbols used in a
  language
• Syntax Specification the set of symbols used in
  a language and the legal order that they may
  occur
• GRAMMARS are often used to precisely specify
  syntax of languages

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Some Jargon

• Lexical Analysis analysing the characters that
  make up program/sentence syntax to work out the
  components of the program/sentence
• Eg I f ( x x x x 2 3 4 5 ) y y y 4 2
  ETC
• Are a sequence of characters. After lexical
  analysis this might translate to
• Keyword(if) openbracket identifier(xxxx)
  operator() integer(2345) closedbracket
  Identifier(yyy) operator() integer(42) .

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Some Jargon

• Parsing analysing the components of the
  program/sentence to work out its syntactic
  structure
• IF-construct
• Keyword(if) openbracket identifier(xxxx)
  operator() integer(2345)

Boolean Expression
Statement
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TERM 2 contents

• Theory of Languages revision, Grammars and
  Properties of Grammars
• Lexical Analysis, Scanning
• Parsing
• Automated Parser Generation
• Symbol Tables
• Code Generation

CODE ANALYSIS
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Related Subjects

• Software Design Compilers/interpreters can be
  very complex programs they require good
  software development skills
• Theory of computing A great deal of the theory
  of automata, and grammars, is used to inform the
  practical pursuit of building language
  translators
• Syntax and Semantics of Programs You have to
  know how a language is structured, and what a
  language means before you can write a translator

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Resources for TERM 2

• Main Book Andrew Appel Modern Compiler
  Implementation in Java. There are many copies in
  the library. We will cover the first 100 or so
  pages.
• Other Books There are many books on Compilers
  all are worth looking at for background.
• Website This forms the module hand book, as it
  has most of the teaching resources, the lecture
  plan, and the coursework
• There are links to other resources from the
  website an online book, and some other lecture
  notes
• Lecture Slides, most tutorial/practical sheets
  and most answers to questions are all on the
  website
• NB I may change some of the lecture slides /
  tutorials for this year. The coursework will be
  different also!

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Resources for TERM 2

• The MAIN practical tool for this term is
• JavaCup
• This is a PARSER-GENERATOR
• we will use it to generate parsers automatically
  from syntax specifications

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Tutorial this week

• Find the website
• http//scom.hud.ac.uk/scomtlm/cas380/
• Work through the exercises in Week 1. These are
  REVISION. If you are happy with a question move
  on to the next.
• Some of the answers appear on the website.
• See
• http//www.javaworld.com/javaworld/jw-02-2003/jw-0
  207-java101.html