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Introduction to Language Processors and Compiler Structure

This chapter provides an overview of language processors, focusing on the structure and evolution of compilers. It explores the phases of compilation, including lexical analysis, syntax analysis, semantic analysis, and code generation. The material emphasizes why understanding programming language principles is crucial for software engineers, enhancing their ability to use language features effectively and select appropriate languages for various projects. Additionally, this chapter covers the evolution of programming languages from machine code to modern high-level languages, highlighting their classifications and applications.

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Introduction to Language Processors and Compiler Structure

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  1. Chapter 1. Introduction

  2. Outline • Language Processors • The Structure of a Compiler • The Evolution of Programming Languages • Why study principle of programming languages

  3. Language Processors • A compiler source program Compiler target program

  4. Running the target program Target Program input output

  5. An interpreter • Much slower program execution • Better error diagnostics Interpreter source program output input

  6. A hybrid compiler, e.g. Java source program Translator intermediate program Virtual Machine output input

  7. Outline • Language Processors • The Structure of a Compiler • The Evolution of Programming Languages • Why study principle of programming languages

  8. A Language Processing System source program Preprocessor modified source program Compiler target assembly program Assembler relocatable machine code library filesrelocatable object files Linker/Loader target machine code

  9. The Structure of a Compiler • Analysis • Front end • Using a grammatical structure to create an intermediate representation • Collecting information about the source program in a symbol table • Synthesis • Back end • Constructing the target program from the intermediate representation and the symbol table

  10. Phases of a Compiler character stream Lexical Analyzer token stream SymbolTable Syntax Analyzer syntax tree (optional) Semantic Analyzer syntax tree Machine-Independent Code Optimization Intermediate Code Generator intermediate representation Code Generator Machine-Dependent Code Optimization (optional) target machine code

  11. Lexical Analysis (Scanning) • Grouping characters into lexemes • E.g. • position = initial + rate * 60 • <id,1> <=> <id,2> <+> <id,3> <*> <60>

  12. Syntax Analysis (Parsing) • Creating a tree-like (e.g. syntax tree) intermediate representation that depicts the grammatical structure of the token streams • E.g. • <id,1> <=> <id,2> <+> <id,3> <*> <60> = + <id, 1> * <id, 2> 60 <id, 3>

  13. Semantic Analysis • Type checking • Type conversions or coercions • E.g. = + <id, 1> * <id, 2> <id, 3> int2float 60

  14. Intermediate Code Generation • Generating a low-level intermediate representation • It should be easy to produce • It should be easy to translate into the target machine • E.g. three-address code t1 = int2float(60)t2 = id3 * t1t3 = id2 + t2id1 = t3

  15. Code Optimization • Attempts to improve the intermediate code • Better: faster, shorter code, or code that consumes less power (Chap. 8 -) • E.g. • t1 = id3 * 60.0id1 = id2 + t1

  16. Code Generation • Mapping intermediate representation of the source program into the target language (Chap. 8) • Machine code: register/memory location assignments • E.g. • LDF R2, id3MULF R2, R2, #60.0LDF R1, id2ADDF R1, R1, R2STF id1, R1

  17. Symbol Table Management • To record the variable names and collect information about various attributes of each name • Storage, type, scope • Number and types of arguments, method of argument passing, and the type returned

  18. Grouping of Phases into Passes • Front-end pass • Lexical analysis, syntax analysis, semantic analysis, intermediate code generation • (Optional) Code optimization pass • Back-end pass • Code generation

  19. Outline • Language Processors • The Structure of a Compiler • The Evolution of Programming Languages • Why study principle of programming languages

  20. The Evolution of Programming Languages • Machine language: 1940’s • Assembly language: early 1950’s • Higher-level languages: late 1950’s • Fortran: scientific computation • Cobol: business data processing • Lisp: symbolic computation • Today: thousands of programming languages

  21. Classification of Programming Languages – by Generation • First generation: machine languages • Second generation: assembly languages • Third generation: high-level languages • Fortran, Cobol, Lisp, C, C++, C#, Java • Fourth generation: specific application • NOMAD, SQL, Postscript • Fifth generation: logic- and constraint-based • Prolog, OPS5

  22. Classification of Programming Languages - by Functions • Imperative: how • C, C++, C#, Java • Declarative: what • ML, Haskell, Prolog • von Neumann language • Fortran, C • Object-oriented language • Simula 67, Smalltalk, C++, C#, Java, Ruby • Scripting languages • Awk, JavaScript, Perl, PHP, Python, Ruby, Tcl

  23. Outline • Language Processors • The Structure of a Compiler • The Evolution of Programming Languages • Why study principle of programming languages

  24. Why study principle of programming languages? • Become a better software engineer • Understand how to use language features • Appreciate implementation issues • Better background for language selection • Familiar with range of languages • Understand issues / advantages / disadvantages • Better able to learn languages • You might need to know a lot

  25. Why study programming languages? • Better understanding of implementation issues • How is “this feature” implemented? • Why does “this part” run so slowly? • Better able to design languages • Those who ignore history are bound to repeat it…

  26. End of Chapter 1

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