Programming Language Evolution and Study

1. Chapter 1 :: Introduction Origin : Michael L. Scott School of Computer & Information Engineering, Sangji University KwangmanKo (kkman@sangji.ac.kr)

2. Reading 1, P40. • Reading 2, P40

3. 1. Introduction, P41 • Why are there so many programming languages? • evolution - we've learned better ways of doing things over time • socio-economic factors: proprietary interests, commercial advantage • orientation toward special purposes • orientation toward special hardware • diverse ideas about what is pleasant to use

4. Introduction • What makes a language successful? , PP42-43. • easy to learn(BASIC, Pascal, LOGO, Scheme) • easy to express things, easy use once fluent, "powerful” • C, Common Lisp, APL, Algol-68, Perl, … • easy to implement (BASIC, Forth) • possible to compile to very good (fast/small) code (Fortran) • backing of a powerful sponsor (COBOL, PL/1, Ada, Visual Basic) • wide dissemination at minimal cost (Pascal, Turing, Java)

5. 1.2 Program Language Spectrum, PP45-46. • Classified into families based on Model of Computation • Declarative Programming Language • focused on WHAT the computer is to do. • More higher level, tune with the programmer’s point of view. • Imperative Programming Language • focused on HOW the computer should do it. • dominate, mainly for performance reasons

6. Declarative programming language • Functional • Scheme, ML, pure Lisp, FP, … • logic, constraint-based: • Prolog, VisiCalc, RPG, … • Imperative programming language • von Neumann: • Fortran, Pascal, Basic, C, … • object-oriented: • Smalltalk, Eiffel, C++, … • scripting languages: • Perl, Python, JavaScript, PHP, …

7. 1.3 Why study programming languages?, P47~ • Help you choose a language. • for systems programming • C vs. Modula-3 vs. C++ • for numerical computations • Fortran vs. APL vs. Ada • for embedded systems • Ada vs. Modula-2 • for symbolic data manipulation • Common Lisp vs. Scheme vs. ML • for networked PC programs • Java vs. C/CORBA

8. Reading, P48. • Understand OBSCURE features: • Choose among alternative ways to express things • understand implementation costs • Make good use of debuggers, assemblers, linkers, and related tools • Simulate useful features in languages that lack them

9. 1.4 Compilation vs. Interpretation • Compilation vs. Interpretation • not opposites • not a clear-cut distinction Input Data Compiler Target Program Source Program Outputs Source Program Interpreter Outputs Input Data

10. Compilation vs. Interpretation • Pure Compilation • translates the high-level source program into an equivalent target program(typically in machine language). COMPILER 원시 프로그램 Frontend 중간코드 Backend 목적 프로그램

11. Pure Interpretation • stays around for the execution of the program • the locus of control during execution • Reading, P51. • Interpretation • Greater flexibility • Better diagnostics (error messages) • Compilation • Better performance

12. Most language implementations, ☞ P 51. • a mixture of both compilation and interpretation • compilation or simple pre-processing, followed by interpretation source program translator Virtual Machine (interpreter) intermediate program Output Input Data

13. source program Test.java Java compiler (javac Test.java ) translator Virtual Machine (interpreter) Java interpreter (java Test.class) Test.class intermediate program Output Input Data

14. Preprocessor • Removes comments and white space • Groups characters into tokens (keywords, identifiers, numbers, symbols) • Expands abbreviations in the style of a macro assembler • Identifies higher-level syntactic structures (loops, subroutines)

15. Library of Routines and Linking • Reading, P52. • Compiler uses a linker program to merge the appropriate library of subroutines (e.g., math functions such as sin, cos, log, etc.) into the final program: source program compiler Incomplete machine program Library Routines LINKER machine program

16. Post-compilation Assembly • Facilitates debugging (assembly language easier for people to read) • Isolates the compiler from changes in the format of machine language files (only assembler must be changed, is shared by many compilers)

17. The C Preprocessor (conditional compilation) • Preprocessor deletes portions of code, which allows several versions of a program to be built from the same source

18. Source-to-Source Translation (C++) • C++ implementations based on the early AT&T compiler generated an intermediate program in C, instead of an assembly language:

19. Bootstrapping

20. Dynamic and Just-in-Time(JIT) Compilation • Reading, P56. • In some cases a programming system may deliberately delay compilation until the last possible moment. • The Java language definition defines a machine-independent intermediate form known as byte code. Byte code is the standard format for distribution of Java programs. • The main C# compiler produces .NET Common Intermediate Language (CIL), which is then translated into machine code immediately prior to execution.

21. Compilation vs. Interpretation • Tools

22. 1.5 Programming Environments

23. 1.6 An Overview of Compilation, PP59-60.