SYSTEMSDESIGNANALYSIS 1 Chapter 20 Software Engineering Jerry Post Copyright © 1997

SYSTEMSDESIGN 2 Software Quality  User Validation  Bug free  Maintainability  Total Quality Management  Plan for quality.  Do not tolerate sloppy work.  Do it right the first time.  Modularity.  Standards.  Building for Quality  User involvement  Structured walkthrough  Systems methodologies  Top Down  Business goals, functions, operations, systems.  Difficulty: hard to finish the analysis.  Bottom Up  Databases and programs built as needed.  Difficulty: hard to coordinate and combine systems.  Standards.

SYSTEMSDESIGN 3 Top Down and Bottom Up Management Functions Operations Databases Programs Functions Operations Databases Programs  Identify Management  Functions &  Operations  Entire Organization  Design Systems  Data  Programs  Standards!  Integrate  Write code  Build DB  Find a problem

SYSTEMSDESIGN 4 Structure Charts 200 Add New Employee Record 210 Read New Employee Record 220 Edit New Employee Record 230 Print Valid Employee List or Message 240 Write Valid Employee Record New Employee Record EOF Switch New Employee Record Valid Employee Flag Valid Employee Flag New Employee Record New Employee Record Control flags Data couple/pass Avoid passing decision flags downward. Make the decision at higher level.

SYSTEMSDESIGN 5 Structure Chart Symbols Repeat one or more sub-modules. Some, but not all sub-modules will be performed. Loop Condition

SYSTEMSDESIGN 6 Hierarchy Input/Process/Output Charts (HIPO)  Top Down approach  VTOC, visual table of contents, Hierarchy.  Overview IPO diagrams.  Detailed IPO diagrams. Inventory Update and Report1.0 Inventory Update 2.0 Process Reporting 3.0 Transaction Entry 2.1 Transaction Validation 2.2 Edit Transaction 2.3 Update File 2.4

SYSTEMSDESIGN 7 IPO Diagram Old Inventory File Transaction Record Provide for data entry; validate transactions to insure transaction type and part number are correct; edit all incorrect transactions; modify inventory file. Generate daily inventory report; generate the summary reports. New Inventory File Backorder File Daily Inventory File Summary Report InputProcessOutput

SYSTEMSDESIGN 8 Program/Process Diagramming Tools  Visual Table of Contents (VTOC)  Input-Process-Output (IPO)  System flowchart  Nassi-Shneiderman Charts  Warnier-Orr Diagrams  Drawbacks  Diagrams waste space.  Many people do not know how to read the diagrams.  Lack of standards.  Generally better to use pseudocode!

SYSTEMSDESIGN 9 Manuals and Documentation  Procedure Manuals  Explanation for users and operators.  Background comments.  Steps to perform a process.  Help for recovering from problems.  Trouble-shooting.  On-line, hypertext, and searchable.  Technical writing style.

SYSTEMSDESIGN 10 Computer-Aided Software Engineering (CASE)  Maintain documents.  Joint development.  Generate code and applications.  Reverse engineering.

SYSTEMSDESIGN 11 Testing  Testing methods  Test data.  Link testing.  Full systems test. Sample data. Live data.  Bugs flock together.  Maintenance practices  Modifications almost always cause additional problems.  Fixing one bug causes more bugs.  Feedback from users.  Auditing  Test procedures.  Test users and operators.  Evaluate controls.