ISBN 程序设计语言原理 谭文安 南京航空航天大学 信息科学与技术学院

1-2 主要参考书 Concepts of Programming Languages ( Sixth Edition ) Robert W. Sebesta ，机械工业出版社， 2002 程序设计语言：设计与实现 Terrence W.Pratt, Matvin V.Zelkowitz 傅育熙，黄林鹏等译，电子工业出版社， 2002 程序设计语言概念和结构 Ravi Sethi 著, 裘宗燕等译，机械工业出版社， 2002 程序设计语言原理 钱树人， 高等教育出版社， 2001

1-3 教学环节和成绩评定 教学环节：课堂讲授 课外阅读 成绩评定：期末考试 + 偶尔点名

1-4 Chapter 1 Topics Motivation Programming Domains Language Evaluation Criteria Influences on Language Design Language Categories Language Design Trade-Offs Implementation Methods Programming Environments

1-5 Motivation: Why Study Programming Languages? Increased ability to express ideas Improved background for choosing appropriate languages Greater ability to learn new languages Understand significance of implementation Ability to design new languages Overall advancement of computing

1-6 Programming Domains Scientific applications –Large number of floating point computations –Fortran90  Algol60 … Business applications –Produce reports, use decimal numbers and characters –COBOL Language … Artificial intelligence –Symbols rather than numbers manipulated –LISP （函数式的）, Prolog 语言，逻辑程序设计 Systems programming –Need efficiency because of continuous use –Unix OS, C 语言函数 Scripting languages –Put a list of commands in a file to be executed –Shell 命令文件,…,JavaScript 语言 (Netscape) Special-purpose languages

1-7 Language Evaluation Criteria Readability –The most important criteria –Factors: Overall simplicity –Too many features is bad ； count++; ++count, 运算符重载 Orthogonality 正交性 –Makes the language easy to learn and read –Meaning is context independent –A relatively small set of primitive constructs can be combined in a relatively small number of ways –Every possible combination is legal –Lack of orthogonality leads to exceptions to rules

1-8 Language Evaluation Criteria –Readability factors (continued) Control statements –Goto 语句 Defining data types and structures –Boolean 变量定义 True/False 1/0 – 数组定义, 下标变量 Syntax considerations –Identifier forms Fortran77 标示符长度 <=6 –Special words Pascal 的 begin – end Ada 的 end if, end loop Fortran 90 中, DO 和 END 是合法的变量名

1-9 Language Evaluation Criteria Writability— 可写性 –Factors: Simplicity and orthogonality Support for abstraction( including data & procedure ) Expressivity 表达性 Reliability— 可靠性 –Factors: Type checking 函数调用参数传递 Exception handling 异常处理能力 Aliasing 别名使用是一个危险的特性 Readability and Writability

1-10 Language Evaluation Criteria Cost –Categories Training programmers to use language Writing programs Compiling programs Executing programs Language implementation system Reliability Maintaining programs

1-11 Influences on Language Design Computer architecture: Von Neumann We use imperative languages, at least in part, because we use von Neumann machines –Data and programs stored in same memory –Memory is separate from CPU –Instructions and data are piped from memory to CPU –Basis for imperative languages Variables model memory cells Assignment statements model piping Iteration is efficient

1-12 Von Neumann Architecture

1-13 Influences on Language Design Programming methodologies –1950s and early 1960s: Simple applications; worry about machine efficiency –Late 1960s: People efficiency became important; readability, better control structures Structured programming Top-down design and step-wise refinement –Late 1970s: Process-oriented to data-oriented data abstraction –Middle 1980s: Object-oriented programming

1-14 Language Categories Imperative -- 命令式语言 –Central features are variables, assignment statements, and iteration –C, Pascal Functional -- 函数式语言 –Main means of making computations is by applying functions to given parameters –LISP, Scheme

1-15 Language Categories Logic -- 逻辑语言 –Rule-based –Rules are specified in no special order –Prolog Object-oriented -- 面向对象语言 –Encapsulate data objects with processing –Inheritance and dynamic type binding –Grew out of imperative languages –C++, Java

1-16 Language Design Trade-Offs Reliability vs. cost of execution ( Eg. Ada ) Readability vs. writability Flexibility vs. safety

1-17 Layered View of Computer

1-18 Implementation Methods Compilation –Translate high-level program to machine code –Slow translation –Fast execution

1-19 Compilation Process

1-20 Implementation Methods Pure interpretation –No translation –Slow execution –Becoming rare

1-21 Pure Interpretation

1-22 Implementation Methods Hybrid implementation systems –Small translation cost –Medium execution speed

1-23 Hybrid Implementation System

1-24 Programming Environments The collection of tools used in software development UNIX –An older operating system and tool collection Borland JBuilder –An integrated development environment for Java Microsoft Visual Studio.NET –A large, complex visual environment –Used to program in C#, Visual BASIC.NET, Jscript, J#, or C++