1. Chapter 7 Program Development & Programming Languages 國立聯合大學 電子工程學系 蕭裕弘

2. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 2 / 45 Chapter Goals  介紹利用電腦解決問題的方法與開發 軟體的程序  介紹程式語言的分類與歷史  介紹程式語言的特性  介紹數種常見的程式語言  介紹語言的轉譯方式  介紹一些不屬於程式語言的電腦語言

3. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 3 / 45 1. Introduction  Problem solving The act of finding a solution to the perplexing ( 令人費解的 ), distressing ( 令人煩惱的 ), vexing ( 傷腦筋的 ), or unsettled question.  To solving the problem, you must answer the following questions: What do I know about the problem? What is the information that I have to process in order to find the solution? What does the solution look like? What sort of special cases exist? How will I recognize that I have found the solution?

4. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 4 / 45 Computer Problem-Solving 問題描述與分析 設計演算法 開發軟體 程式執行與維護

5. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 5 / 45 Problem Specification and Analysis  Problem specification is to have a clear description of the problem Easily done in CS courses for small problems. More difficult to obtain in the real world for large problems.  Analysis is to obtain a clear understanding of the problem Carefully state the objectives of the program What output should the program produce and in what format? What is the nature and format of the required input? Identify the computations required

6. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 6 / 45 Divide and Conquer  Break up a large problem into smaller units that we can handle.  Example: search 15 in the following sequence  Method 1: Linear search from the first number 7 comparisons needed  Method 2: Binary search 4 comparisons needed 12345678910 3589 1315161820

7. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 7 / 45 2. Algorithms  We use algorithms every day Arithmetic operations Dialing a phone Looking up a phone number in the phone book Changing a tire …  Usually, algorithm means a precise method in information processing. 拿起話筒 按下一個 號碼鍵 是否按了 九個號碼 ？ No Yes Start Stop

8. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 8 / 45 Definition of Algorithm  An algorithm is a well-defined set of instructions, finite in number, for accomplishing some task which, given a set of inputs, will result in some recognizable end-state.  Every algorithm must satisfy the following criteria: Input: there are zero or more quantities which are externally supplied; Output: at least one quantity is produced; Definiteness: each instruction must be clear and unambiguous; Finiteness: if we trace out the instructions of an algorithm, then for all cases the algorithm will terminate after a finite number of steps; Effectiveness: every instruction must be sufficiently basic that it can in principle be carried out by a person using only pencil and paper.

9. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 9 / 45 Algorithm Design  Algorithm design tools include Structure charts Flowcharts Pseudocode Algorithms + Data Structures = Programs Program control InputCalculateOutput Start Input data Calculate result Output result Stop Input the data; Calculate the result; Output the result;

10. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 10 / 45 常用的流程圖符號 開始 / 結束 決策判斷 印表機輸出 磁碟 儲存資料 處理 輸入 / 輸出 流程方向 連結點

11. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 11 / 45 Example of Flowchart  以迴圈 (loop) 方式計算 1 + 2 +... + N 的值。  執行過程 : 1 (sum = 0), 2 (N = 3), 3 (i = 0) 4 (Yes), 6 (i = 1, sum = 1), 4 (Yes), 6 (i = 2, sum = 3), 4 (Yes), 6 (i = 3, sum = 6), 4 (No), 5 (sum = 6) Start Input N sum = 0 i = 0 i < N ? i = i + 1 sum = sum + i Output sum Stop 1234512345 6 Yes No

12. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 12 / 45 Example of Pseudocode  Goal: find the largest number in a number list 1.Pretend the first number in the list is the largest number. 2.Look at the next number, and compare it with this largest number. 3.Only if this next number is larger, then keep that as the new largest number. 4.Repeat steps 2 and 3 until you have gone through the whole list. Given: a list "List" largest = List[1]; counter = 2; while (counter <= length(List)) if (List[counter] > largest) largest = List[counter]; counter = counter + 1; print largest;

13. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 13 / 45 Software Development  Five phases are common in software development Problem Specification and Analysis Design of solution Implementation or Coding Testing, Execution, and Debugging Maintenance Software Development Life Cycle (SDLC)

14. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 14 / 45 Software Development Methods - 1  In the top-down model, an overview of the system is formulated, without going into detail for any part of it. Each part of the system is then refined by designing it in more detail. Each new part may then be refined again, defining it in yet more detail until the entire specification is detailed enough to begin development.  Top down approaches emphasize planning, and a complete understanding of the system. It is inherent that no coding can begin until a sufficient level of detail has been reached on at least some part of the system. Command interpret system Read command Evaluate command Display result Parse command Dispatch command Look-upType fileDelete file

15. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 15 / 45 Software Development Methods - 2  In the bottom-up design, individual parts of the system are specified in detail, and may even be coded. The parts are then linked together to form larger components, which are in turn linked until a complete system is arrived at.  Bottom up emphasizes coding, which can begin as soon as the first module has been specified.  However bottom-up coding runs the risk that modules may be coded without having a clear idea of how they link to other parts of the system, and that such linking may not be as easy as first thought.

16. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 16 / 45 Choosing a Programming Language  Factors that may affect the decision of choosing a programming language: Suitability Integration Standards Programmer availability Portability Speed C Java PHP C++ COBOL FORTRAN BASIC

17. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 17 / 45 2. Programming Languages  A programming language or computer language is a standardized communication technique for expressing instructions to a computer.  A programming language is a set of syntactic and semantic rules used to define computer programs.  A programming language enables a programmer to precisely specify what data a computer will act upon how these data will be stored/transmitted precisely what actions to take under various circumstances

18. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 18 / 45 Purpose of Programming Languages  A primary purpose of programming languages is to enable programmers to express their intent for a computation more easily than they could with a lower-level language or machine code.  For this reason, programming languages are generally designed to use a higher-level syntax, which can be easily communicated and understood by human programmers.  Programming languages are important tools for helping software engineers write better programs faster.  Understanding programming languages is crucial for those engaged in computer science, because all types of computation are done with computer languages today.

19. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 19 / 45 History of Programming Languages

20. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 20 / 45 Generations of Programming Languages - 1 GenerationsRepresentativeFeaturesExamples 1 Machine language Numerically coded instructions to the CPU Machine-specifically 0101011010 2 Assembly languages Mnemonics for the designation of machine instructions elementary math. and logs. Functions branches, subroutines ADD, SUB, MUL, DIV, JUMP, CALL, … 3 (1st phase) Procedural languages First high-level languages processing of character strings, higher mathematical functions Fortran, Basic

21. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 21 / 45 Generations of Programming Languages - 2 GenerationsRepresentativeFeaturesExamples 3 (2nd phase) Structured languages Structured programming iterations, case branches etc. Pascal, C 4 Object-oriented languages Object-oriented programming data encapsulation inheritance polymorphism C++, Object Pascal 5 Component- based (visual) languages Visual programming components, events, two way tools (rapid application development - RAD) Delphi, Java, C++ Builder, (Visual Basic)

22. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 22 / 45 Generations of Programming Languages - 3 GenerationYearRepresentativeExamples 11945 Machine language 2Mid-1950s Assembly language 3Early 1960s High-level languages FORTRAN, COBOL, BASIC, C, Ada 4Early 1970s Very-high-level languages SQL 5Early 1980s Natural languages

23. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 23 / 45 3. Features of a Programming Language  Each programming language can be thought of as a set of formal specifications concerning syntax, vocabulary, and meaning.  These specifications usually include: Data type and data structures Instruction and control flow Reference mechanisms and re-use Design philosophy

24. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 24 / 45 Data Types and Data Structures  The particular system by which data are organized in a program is the type system of the programming language. Primitive data types  Data types with which values have a one-to- one correspondence to data objects stored in computer memory.  Primitive types are also known as built-in types or basic types.  In C: char, int, float, double Structured data types or composite data types  Data type made up of more primitive types.  Values with a composite type are stored in the memory in such a way that each attribute is followed by another attribute.  In C: array, struct, … Data typeMemory used char1 bytes int2 or 4 bytes float4 bytes double8 bytes

25. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 25 / 45 Variables  In computer science, a variable is a symbol denoting a quantity or symbolic representation.  A variable can be thought of as a place to store a value in computer memory.  When one begins using a given variable, the language interpreter or compiler typically sets aside a space in memory to store the value given to that variable. charch; inttotal; floataverage; intchi; inteng; ch total average

26. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 26 / 45 Instructions and Statements  Once data has been specified, the machine must be instructed how to perform operations on the data.  Elementary statements may be specified using keywords or may be indicated using some well-defined grammatical structure.  Each language takes units of these well-behaved statements and combines them using some ordering system. Depending on the language, differing methods of grouping these elementary statements exist. total = chi + eng + ari; average = total / 3.0;

27. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 27 / 45 Control Flow  Furthermore, beyond the data manipulation instructions, other typical instructions in a language are those used for control flow. Branches Loops Score >= 60 ? Yes No Output ‘pass’Output ‘fail’ Repeat? No Yes Statement 2 Statement 1 Statement 2

28. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 28 / 45 Reference Mechanisms and Re-use  The core of the idea of reference is that there must be a method of indirectly designating storage space.  The most common method is through named variables.  Depending on the language, further indirection may include references that are pointers to other storage space stored in such variables or groups of variables.  Similar to this method of naming storage is the method of naming groups of instructions. Most programming language use procedure calls or function calls as the statements that use these names. Using symbolic names in this way allows a program to achieve significant flexibility, as well as a high measure of reusability. Calls function A Body of function A Subroutine Procedure Function

29. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 29 / 45 Design Philosophy  For different purposes, each language has been developed using a special design or philosophy.  Some aspect or another is particularly stressed by the way the language uses data structures, or by which its special notation encourages certain ways of solving problems or expressing their structure.

30. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 30 / 45 4. Language Translators  Since the computer can only execute the program in machine code, the programs written in assembly or high-level language should be translated into machine code before execution.  Types of language translators: Assembler Compiler Interpreter Source program Translator Object code or results

31. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 31 / 45 Assembler  Assembly language is a human-readable notation for the machine language that a specific computer architecture uses.  Every computer architecture has its own machine language, and therefore its own assembly language.  An assembler is a computer program for translating assembly language into object code. mov al, 0x6110110000 01100001 Instruction = Operation code + Operand(s)

32. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 32 / 45 Compiler  A compiler is a computer program that translates a computer program written in one computer language (called the source language) into a program written in another computer language (called the output or the target language).  Most compilers translate source code written in a high level language to object code or machine language that may be directly executed by a computer or a virtual machine.  The first completed compiler: 1950s FORTRAN Lexical analysis Syntax analysis Semantic analysis Intermediate code generation Optimization Code generation

33. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 33 / 45 Process of Compilation inta, b, c; floatd; c = a + b; d = (a + b) / (a - b); inta, b, c; floatd; c = a + b; d = ( a + b ) / ( a - b ); Allocate.Ia Allocate.Ib Allocate.Ic Allocate.Fd Loadr1, a Loadr2, b Addr3, r1, r2 Storec, r3 Loadr4, a Loadr5, b Addr6, r4, r5 Subr7, r4, r5 Div.Fr8, r6, r7 Stored, r8

34. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 34 / 45 Linkage Editor  A linker or linkage editor is a program that takes one or more objects generated by compilers and assembles them into a single executable program. CompilerSource #1Object #1 CompilerSource #2Object #1 CompilerSource #nObject #n System library Linker Load module

35. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 35 / 45 Interpreter  An interpreter is a computer program that executes other programs.  Interpreting code is slower than running the compiled code because the interpreter must analyze each statement in the program each time it is executed and then perform the desired action whereas the compiled code just performs the action. High-level source program Load Source Program In memory Run Interpreter translates one instruction Machine- code instruction Execute

36. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 36 / 45 5. Popular PLs - FORTRAN  The name is short for Formula Translator/Translation.  Fortran is mainly used for scientific computing and numerical analysis.  Although originally a procedural language, recent versions of Fortran have included some features to support object-oriented programming. PROGRAM HELLO PRINT *, 'hello, world' END

37. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 37 / 45 COBOL  Its name is an acronym, for COmmon Business Oriented Language.  Its primary domain was in business, finance, and administrative systems for companies and governments. ENVIRONMENT DIVISION. DATA DIVISION. PROCEDURE DIVISION. BEGIN. DISPLAY " " LINE 1 POSITION 1 ERASE EOS. DISPLAY "HELLO, WORLD." LINE 15 POSITION 10. STOP RUN. EXIT.

38. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 38 / 45 Pascal  Pascal is based on the Algol programming language and is named in honor of mathematician and philosopher Blaise Pascal.  Pascal is one of the landmark programming languages on which generations of students cut their teeth and variants of which are still widely used today. program HelloWorld; Begin WriteLn('Hello World!') end.

39. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 39 / 45 BASIC, Visual BASIC  BASIC's name stands for Beginner's All-purpose Symbolic Instruction Code.  Originally devised as an easy-to-use tool, it became widespread on home microcomputers in the 1980s, and remains popular to this day in a handful of heavily evolved dialects.  BASIC is available on nearly every microprocessor platform made: Interpret version Compile version 10 PRINT “Hello World!”

40. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 40 / 45 C, C++, C#  C has since spread to many other operating systems, and is one of the most widely used programming languages.  C is prized for its efficiency, and is the most popular programming language for writing system software, though it is also used for writing applications.  It is also commonly used in computer science education, despite not being designed for novices. #include int main(void) { printf("Hello, World!\n"); return 0; }

41. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 41 / 45 Java  The Java language is an object-oriented programming language created by James Gosling and other engineers at Sun Microsystems in 1991.  There were four primary goals in the creation of the Java language: It is object-oriented. It is independent of the host platform (more or less). It contains language facilities and libraries for networking. It is designed to execute code from remote sources securely. import java.io.* public class Print { public static void main(String args[]) { System.out.println(“Hello, World!”); }

42. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 42 / 45 6. Other Languages - HTML  HyperText Markup Language (HTML) is a markup language designed for creating web pages, that is, information presented on the World Wide Web.  HTML tags can be used to perform such tasks as: Declaring titles for page, Identifying the size of headings,, Marking the ends of paragraphs, Establishing such text styling as italic and boldfaced type,, Setting up hyperlinks to other documents, Identifying complex elements to be inserted into a document, such as images, video clips, and sound files, Specifying the layout of tables and frames,

43. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 43 / 45 JavaScript  JavaScript is an object-oriented scripting language commonly used in websites.  It was originally developed by Brendan Eich of Netscape Communications under the name "Mocha" and then "LiveScript" but then renamed to "JavaScript" and given a syntax closer to that of Sun Microsystems’ Java language. document.write("Hello World!");

44. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 44 / 45 VBScript  VBScript (short form of Microsoft's Visual Basic Scripting Edition) is a subset of Visual Basic used in Active Server Pages and in Windows Scripting Host as a general-purpose scripting language.  VBScript is interpreted by a script engine: ASP in a web environment wscript.exe in a Windows environment cscript.exe in a command-line environment. msgbox "Hello world!"

45. 國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: Page 45 / 45 PHP  PHP (a recursive acronym for "PHP: Hypertext Preprocessor") is a widely- used open-source programming language primarily for server-side applications and developing dynamic web content.  PHP's ease of use and similarity with the most common structured programming languages – most notably C and Perl. <? echo "Hello World! " ; ?>