Chapter 10 Software Programming - cs.kent.edudreed/CS10001/Archives/Fall_2007/Notes/ch_10_full… · Design Development & ... Chapter 10: Software Programming 12 Program Development

Chapter 10: Software Programming 1

Chapter 10Software Programming

CS10001 – Computer Literacy


Discussion Topics System development life cycle Life cycle of a program Problem statement Algorithms Moving from algorithm to code Moving from code to machine language Testing programs Completing a program Selecting the right programming language Most popular programming languages


Information Systems System A collection of pieces working together to

achieve a common goal

An information system includes Data People Procedures Hardware/Software

System development life cycle (SDLC) An organized process (or set of steps) used to

develop systems in an orderly fashion


System Development Life Cycle

Problem/ Opportunity Identification

Analysis

DesignDevelopment

& Documentation Testing

& Installation Maintenance

& Evaluation

One step is completed before proceeding to the next.


SDLC Step #1:Problem/Opportunity Identification

The existing system is evaluated: Problems are defined

New proposals are reviewed

Decisions are made to proceed with the

projects

Document the process and relevant

problems/opportunities defined


SDLC Step #2:Analysis

A program specification is developed

(goals and objectives of the project are clearly stated)

Feasibility assessment is performed (should the project move forward)

User requirements are defined

Analysts recommend a plan of action

The plan is documented


SDLC Step #3:Design

A detailed plan for programmers is developed Flowcharts and data-flow diagrams are used for the

current and proposed system Document the design

Data-flow diagram

Flowchart


SDLC Step #4:Development & Documentation

Actual programming takes place

First phase of the program development life cycle (PDLC)

Development is documented

User documentation is created


SDLC Step #5:Testing & Installation

Testing the program for proper operation

Installation of the program for use

Document testing and results


SDLC Step #6:Maintenance & Evaluation

Performance of the system is monitored

Corrections and modifications to the program are made (program bugs)

Document maintenance procedures and results


The Life Cycle of a Program

Programming is the process of translating a task into a series of commands a computer will use to perform that task.

Programming involves: Identifying the parts of a task the computer can

perform. Describing tasks in a specific and complete

manner. Translating the tasks into a language that is

understood by the computer’s CPU.


Program Development Life Cycle

Step 5Finishing the Project

Step 4Debugging

Step 3Coding

Step 2Making a Plan

Step 1Describing the Problem


PDLC Step 1 : Describing the Problem

The problem statement is: The starting point of programming A description of tasks the program is to

accomplish How the program will execute the tasks Created through interaction between the

programmer and the user

The program statement includes error handling and a testing plan


Parking Garage Example

Error message/ask user to reenter value

Handling error

8*7.32 + 4*11.73 Testing overtime input

3*7.32 Testing positive input

8*7.32 Testing positive input

OUTPUT NOTES

–6

12

3

8

INPUTTESTING PLAN:

The input Number of Hours Worked must be a positive real number. If it is a negative number or other nonacceptable character, the program will force the user to reenter the information.

ERROR HANDLING:

The Total Pay Earned is computed as $7.32 per hour for the firsteight hours worked each day. Any hours worked beyond the first eight are billed at $11.73 per hour.

PROCESS:

Total Pay Earned ................................... a positive numberOUTPUTS:

Number of Hours Worked........................ a positive numberINPUTS:

To compute the total pay for a fixed number of hours worked at a parking garage.

PROGRAM GOAL:


PDLC Step #2: Making a Plan

Develop an algorithm: A set of specific, sequential steps that

describe what the computer program must do

Complex algorithms include decision points: Binary (yes/no) Loop (repeating actions)

Visual tools used to track algorithm and decision points include:


Flowchart and Pseudocode

Flowchart

Underlined words are information items that appear repeatedly in the algorithm.

1. Ask the user how many hours they worked today

2. If the number of hours worked < = 8, compute total pay without overtime otherwise, computetotal pay with overtime pay

3. Print total pay

Bold terms show actions that are common in programming, such as reading data, making decisions, printing, and so on.

Pseudocode


Top-Down Design

Problem is divided into a series of high-level tasks

Detailed subtasks are created

Subtasks are refined into an algorithm or instruction sequence


Top-Down Design

Tasks Subtasks Algorithm


Object-Oriented Analysis Classes are identified (categories of inputs;

nouns) Data (information; adjectives) Methods or behaviors (actions; verbs)

Objects are defined by their class, data, and behavior

Interaction between classes is determined Existing classes can be used for other

projects Leads to reusability


Object-Oriented Analysis

Adjectives

Verbs

Nouns


PDLC Step #3: Coding

Coding is translating an algorithm into a programming language

Generations of programming languages


Writing the Program

Variable declarations signal the operating system that storage is needed in RAM

Variables are created for all inputs and outputs Amount of running RAM needed Space is determined by the variable’s

data type


Compiling the Program

Compilation is the process of converting code into machine language

A compiler reads the source code and translates it into machine language

After compilation, programmers have an executable program


Interpreting the Program An interpreter translates source code into

a line by line intermediate form Each line is executed before the next line is

compiled Programmers do not have to wait for the

entire program to be recompiled each time they make a change

Programmers can immediately see the results of changes as they are making them in the code


PDLC Step #4: Debugging

Running a program to find errors is known as debugging

Sample inputs are used to determine runtime (logic) errors

Debugger: Tool that helps programmers locate runtime errors


PDLC Step #5: Finishing the Project

Users test the program (internal testing) Beta version released: Information collected about errors before final

revision

Software updates (service packs): Problems found after commercial release

Documentation created: User manuals User training


Programming Languages

Selecting the right language: Space available Speed required Organizational resources available Type of target application

Visual Basic

C / C++ JavaHTML

JavaScriptVBScript

ASP / JSP

Flash / XML


Visual Basic Used to build Windows applicationsObject-oriented languageVisual Basic 2005 is the current

version

Sample Visual Basic


C and C++ C Developed for

system programmers

Combines high and low level programming features

Modern operating systems written in C

C++ Uses the same

features as C Includes object-

oriented design

Sample C

Sample C++


Java

Object-oriented features

Large set of existing classes

Architecture neutral

Java applets: Small Java-based programs


Web Applications

HTML/XHTML Hypertext Markup Language/Extensible

Hypertext Markup Language Not a true programming language Uses special symbols (tags) to control

how Web pages are viewed

Extensible Markup Language (XML) Enables computers to efficiently transfer

information between Web sites


Web Applications JavaScript Used to make Web pages more visually appealing

and interactive

VBScript A subset of Visual Basic Used to add interactivity to Web pages

PHP Another scripting language gaining popularity

Dynamic Decision Making Web page has the ability to display content based

on user choices


Web Applications

Active Server Pages (ASP) and Java Server

Pages (JSP)

Adds interactivity capabilities to Web pages

Translates user information into a request for more information from a company’s computer

Flash

Enables elaborate animations to be created for Web pages

Documents

Chapter 10 Software Programming - cs.kent.edudreed/CS10001/Archives/Fall_2007/Notes/ch_10_full… · Design Development & ... Chapter 10: Software Programming 12 Program Development