S/W Programming & Languages

Chapter 10

Where Your Software Comes From

© The McGraw-Hill Companies, Inc., 2000

2 CCI © The McGraw-Hill Companies, Inc., 2000Ch 10

Overview

• Programming– five steps

• Five generations

• High-level programming

• Object-oriented programming

• Internet programming

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Programming

• What are the five steps of the program-development cycle?

Ch 10 © The McGraw-Hill Companies, Inc., 2000 4 CCI

A Program

• Also called software• List of instructions that processes data into

information• Should include software engineering

– only partly involves coding or using the programming vocabulary

• Languages– Visual Basic, Java, C++, COBOL

Ch 10 © The McGraw-Hill Companies, Inc., 2000 5 CCI

Programming Steps

• Analysis

• Design

• Code

• Test

• Document

• Maintain

Ch 10 © The McGraw-Hill Companies, Inc., 2000 6 CCI

Analysis

• Clarify objectives and needs– on all levels of an organization that the program

may affect

• Clarify outputs– overall performance– response time– forms and reports

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Analysis Is Clarifying

• Clarify inputs– kind and format of input data– insure exception data handled properly

• ask again what exceptions or data is out of the norm

– insure good data input through ranges, checks on validity

• Clarify processing– ensure correct processing, including data storage

and the passing of variables or messages between modules and individual programs

Ch 10 © The McGraw-Hill Companies, Inc., 2000 8 CCI

Feasibility Analysis

• Each programming step requires feasibility checks– economic– operational– technical

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Documentation of Analysis

• Documentation– the outcome of analysis is the

Requirements Statement• clarifies

• well defines the inputs and outputs

• is the basis for test cases

Ch 10 © The McGraw-Hill Companies, Inc., 2000 10 CCI

Design the Program• Structured program

– top-down approach, using hierarchy chart

– designs in modules– starts with control structure– as each part is completed, it is

tested preliminary to ensure functionality

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Rules of Modular Design

• Manageable size– less than fifty or so lines each module

• Independent with a single function

• Functions of input and output are clearly defined

• Single entry and exit point

• Returns control to originating module

Ch 10 © The McGraw-Hill Companies, Inc., 2000 12 CCI

Design Details

• Program flowcharts– steps or algorithms

• Control structures

• Pseudocode– narrative form

• Spaghetti code– what happens when you do not

follow proper design methodology

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Four Design Control Structures• Sequence

– step-by-step

• Selection– if-then-else

• Case– single yes or no per choice

• Iteration– looping until a condition is met– looping while a condition is met

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Design’s Walkthrough

• A structured walkthrough– a formal meeting to review step by step– errors, omissions, duplications– general coding, interface, database, security,

documentation, and network standards

Ch 10 © The McGraw-Hill Companies, Inc., 2000 15 CCI

Coding• Select the programming

language– consider language

capabilities, execution speed, and interface capabilities

• Follow syntax– the compiler understands

exactly what you program

Ch 10 © The McGraw-Hill Companies, Inc., 2000 16 CCI

Testing

• Desk checking– walking through the

code while keeping track of variables on a piece of paper, proofreading

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Code Debugging

• Debugging– detecting, locating, and

removing errors• syntax errors, using

program diagnostics or debug utility

• logical errors - incorrect control or functional errors

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The Alpha

• Alpha-testing– in-house testing of code with portions of real-

world, deliberately incorrect inputs and databases, usually modified for practicality

– test cases refer to the Requirements Statement of Analysis

– sometimes performed by the Software Quality Assurance group

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The Beta

• Beta-testing– is traditionally testing a program in

the real-world by those who are likely to use it

– its purpose is to reveal inadequacies and programming bugs in live conditions

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Program Document

• Written, graphic, and electronic descriptions of what a program does, how the program is organized, and programming suggestions for future maintenance

• Customized by level of detail

– programmer, operator, user

• Shift from large manuals to small printed setup documentation, large electronic help files included during program installation, and additional online assistance and updates

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Program Maintenance

• An art in itself

• Requires system and program skills

• Corrective - fix

• Preventive - make better or more efficient

• Enhancement - changes due to regulation or to add additional functionality

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Programming Languages

• Machine language• Assembly languages• High-level languages• Very high-level

languages• Natural Languages

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First Generation

• Machine language

• Used to debug complex code problems by very experienced programmers

• Compilers for the other generations translate to this level for execution

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Second Generation

• Assembly language– more technical– less flexible and user friendly

than higher-level languages– faster

• Some embedded programs are written in assembly

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Third Generation

• COBOL BASIC, C, compilers, interpreters

• less technical, more flexible, more user friendly

• slower

• procedural

• many large legacy systems in banking and finance

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Fourth-Generation

• 4GLs

• Report and application generators, query languages

• Current development

• Non procedural

• Many office suites are written and can be modified easily, such as Microsoft Office and Lotus Suite

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Fifth Generation

• Natural language

• Future development– IBM ViaVoice and

Dragon Speak are the beginning of speech technology

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Language Translators• Assembler

– translates assembly language program into a machine language

• Compiler– takes your written source code into machine

language object code

• Interpreter– converts high-level statements one at a time– allows programming interactively

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Fortran• (FORmula TRANslator)

– advantages• mathematical and scientific use

• portable to other computers

• short and simple

– disadvantages• not efficient at I/O storage

• not as easy to read

• limited non-numeric data expressions

Ch 10 © The McGraw-Hill Companies, Inc., 2000 30 CCI

COBOL• COmmon Business

Oriented Language– extremely readable– advantages

• portable

• easy to understand

• good file handling and I/O

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BASIC

• Beginner’s All-purpose Symbolic Instruction Code– advantage

– easy to use

– disadvantage• slow processing

• many nonstandard versions

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Pascal

• Named after Blaise Pascal, a 17th century French mathematician and philosopher

• Uses structured programming methods– advantages

• easy to learn with extensive graphics programming

• appropriate for scientific use

– disadvantages• limited I/O, hard for business applications

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Object-Oriented and Visual Programming

• Object-oriented programming (“oops”)

• Trees (plant object) output oxygen and shade– processing elements such as water and minerals – responding to light

• Similarly, computer objects should have an output (message)– processing (methods), and variables (attributes)– responding to input (message)

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Objects

• Creating and using objects is a more natural process than structured programming– deal with and interact with objects every day– do not detail in a step-by-step method as often

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Object

• Consists of preassembled code

• Has methods and attributes

• Is encapsulated– can operate without full dependency on other

code

• Can pass messages on to other objects

• Can have objects that have inherited characteristics from the original object

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Object Advantages

• Reuse if put into well-maintained libraries– called class libraries

• Is not dependent on outcomes known in advance– polymorphism

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Even More Advantages

• Can be quickly modified for similar uses– inheritance

• Objects’s effectiveness has been scientifically proven by the Software Engineering Institute at Carnegie Mellon University

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Examples of OOP

• Smalltalk– first OOP

• C++– allows additional flexibility

of programming in C in a structured manner

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Visual Programming

• Use of icons and other tools

• Allows concentration on problem solving

• Responsive to needs to program graphical user interface (GUI)

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Internet Programming

• HTML– HyperText Markup

Language– creating basic Web

pages, tables, and hyperlinks

– Adobe PageMill, Microsoft FrontPage

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XML

• Extensive markup language

• Tags help define pages for searching and provide easier interface to databases

• SoftQuad’s XMetal

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VRML

• Virtual Reality Markup Language, rhymes with “thermal”

• 3D creation

• Netscape Live 3D and Macromedia Dreamweaver

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Java

• For interactive Web pages and small embedded systems

• Can run small portions called applets

• Most hardware platforms have Java virtual machines to interpret Java, allowing greater portability

• Efficiency of Java’s processing increased