1

Chapter 1. Introduction

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Outline

• Language Processors• The Structure of a Compiler• The Evolution of Programming

Languages• Why study principle of programming

languages

3

Language Processors

• A compiler

Compiler

source program

target program

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• Running the target program

Target Programinput output

5

• An interpreter– Much slower program execution– Better error diagnostics

Interpretersource program

inputoutput

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• A hybrid compiler, e.g. Java

Virtual Machine

inputoutput

Translator

source program

intermediate program

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Outline

• Language Processors• The Structure of a Compiler• The Evolution of Programming

Languages

• Why study principle of programming languages

8

A Language Processing System

Compiler

source program

target machine code

Preprocessor

Assembler

Linker/Loader

modified source program

target assembly program

relocatable machine code

library filesrelocatable object files

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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

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Phases of a Compiler

Syntax Analyzer

character stream

target machine code

Lexical Analyzer

Intermediate Code Generator

Code Generator

token stream

syntax tree

intermediate representation

SymbolTable

Semantic Analyzer

syntax treeMachine-Independent

Code Optimization

Machine-Dependent Code Optimization

(optional)

(optional)

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Lexical Analysis (Scanning)

• Grouping characters into lexemes• E.g.

– position = initial + rate * 60– <id,1> <=> <id,2> <+> <id,3> <*>

<60>

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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> *

<id, 3> 60

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Semantic Analysis

• Type checking• Type conversions or coercions• E.g.

– =

<id, 1> +

<id, 2> *

<id, 3>

60

int2float

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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

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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

•

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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

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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

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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

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Outline

• Language Processors• The Structure of a Compiler• The Evolution of Programming

Languages• Why study principle of programming

languages

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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

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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

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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

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Outline

• Language Processors• The Structure of a Compiler• The Evolution of Programming

Languages• Why study principle of programming

languages

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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

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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…

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End of Chapter 1