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

Chapter 7Program Development & Programming Languages

國立聯合大學　電子工程學系蕭裕弘

國立聯合大學電子工程學系 – 計算機概論 – 蕭裕弘 Chapter 7: / 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


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?


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


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


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

1 2 3 4 5 6 7 8 9 10

3 5 8 9 10 13 15 16 18 20


2. Algorithms

We use algorithms every day Arithmetic operations Dialing a phone Looking up a phone number in the phone bo

ok 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


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.


Algorithm Design

Algorithm design tools include Structure charts Flowcharts Pseudocode

Algorithms + Data Structures = Programs

Program control

Input Calculate Output

Start

Input data

Calculate result

Output result

Stop

Input the data;

Calculate the result;

Output the result;


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


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 + 1sum = sum + i

Output sum

Stop

1

2

3

4

5

6

Yes

No


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;


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)


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

Readcommand

Evaluatecommand

Displayresult

Parsecommand

Dispatchcommand

Look-up Type file Delete file


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.


Choosing a Programming Language

Factors that may affect the decision of choosing a programming language: Suitability Integration Standards Programmer availability Portability Speed

CJava

PHP

C++

COBOLFORTRAN

BASIC


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


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.


History of Programming Languages


Generations of Programming Languages - 1

Generations Representative Features Examples

1 Machine language Numerically coded instructions to

the CPU

Machine-specifically

0101011010

2Assembly 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



Generations Representative Features Examples

3 (2nd phase)Structured languages

Structured programming

iterations,

case branches etc.

Pascal, C

4Object-oriented languages

Object-oriented programming data encapsulation inheritance polymorphism

C++, Object Pascal

5Component-based (visual) languages

Visual programming components, events, two way tools (rapid application development - RAD)

Delphi, Java, C++ Builder, (Visual Basic)



Generation Year Representative Examples

1 1945 Machine language

2 Mid-1950s Assembly language

3 Early 1960s High-level languagesFORTRAN, COBOL, BASIC, C, Ada

4 Early 1970s Very-high-level languages SQL

5 Early 1980s Natural languages


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


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-o

ne 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 th

e memory in such a way that each attribute is followed by another attribute.

In C: array, struct, …

Data type Memory used

char 1 bytes

int 2 or 4 bytes

float 4 bytes

double 8 bytes


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.

char ch;

int total;

float average;

int chi;

int eng;

ch

total

average


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;


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 1

Statement 2


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 offunction A

SubroutineProcedureFunction


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.


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

Sourceprogram Translator

Object codeor results


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, 0x61 10110000 01100001

Instruction = Operation code + Operand(s)


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


Process of Compilation

int a, b, c;

float d;

c = a + b;

d = (a + b) / (a - b);

int a, b, c;

float d;

c = a + b;

d = ( a + b ) / ( a - b );

Allocate.I aAllocate.I bAllocate.I cAllocate.F dLoad r1, aLoad r2, bAdd r3, r1, r2Store c, r3Load r4, aLoad r5, bAdd r6, r4, r5Sub r7, r4, r5Div.F r8, r6, r7Store d, r8


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 #1 Object #1

CompilerSource #2 Object #1

CompilerSource #n Object #n

System library

LinkerLoad

module


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-levelsource

program

LoadSource

ProgramIn memory

Run

Interpretertranslates

oneinstruction

Machine-code

instruction

Execute


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


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.


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.


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!”


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 <stdio.h>

int main(void)

{

printf("Hello, World!\n");

return 0;

}


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!”);

}

}


6. Other Languages - HTML

HyperText Markup Language (HTML) is a markup language designed for c

reating 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, <TITLE>

Identifying the size of headings, <H1>, <H2>

Marking the ends of paragraphs, <P>

Establishing such text styling as italic and boldfaced type, <I>, <B>

Setting up hyperlinks to other documents, <A>

Identifying complex elements to be inserted into a document, such as image

s, video clips, and sound files, <IMG>

Specifying the layout of tables and frames, <TABLE>


JavaScript

JavaScript is an object-oriented scripting language commonly used in websi

tes.

It was originally developed by Brendan Eich of Netscape Communications

under the name "Mocha" and then "LiveScript" but then renamed to "JavaS

cript" and given a syntax closer to that of Sun Microsystems’ Java language.

<HTML>

<SCRIPT LANGUAGE="JavaScript">

document.write("Hello World!");

</SCRIPT>

</HTML>


VBScript

VBScript (short form of Microsoft's Visual Basic Scripting Edition) is a sub

set 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!"


PHP

PHP (a recursive acronym for "PHP: Hypertext Preprocessor") is a widely-

used open-source programming language primarily for server-side applicati

ons and developing dynamic web content.

PHP's ease of use and similarity with the most common structured program

ming languages – most notably C and Perl.

<HTML>

<BODY>

<?

echo "Hello World!";

?>

</BODY>

</HTML>

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

Documents

Transcript of Chapter 7 Program Development & Programming Languages 國立聯合大學電子工程學系...

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

Documents

Transcript of Chapter 7 Program Development & Programming Languages 國立聯合大學 電子工程學系...

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

Transcript of Chapter 7 Program Development & Programming Languages 國立聯合大學電子工程學系...