A&D - Design of Software
4 likes1,064 views
This document discusses key concepts in software design including: - Top-down design which involves starting at the highest level components and working down to lower levels in a stepwise refinement process. - Loose coupling and high cohesion are desirable design principles where components have minimal interdependencies and each focuses on a single logical function. - Span of control refers to the number of sub-modules controlled by a main module in software design. - Key concepts are illustrated through diagrams of tight vs loose coupling and examples of how modules can be organized at different levels with sub-procedures.
A&D - Design of Software
- 1. Design of Software Organized By: Vinay Arora Assistant Professor CSED, Thapar University www.slideshare.net/aroravinay
- 2. Disclaimer This is NOT A COPYRIGHT MATERIAL Content has been taken mainly from the following books: System Analysis and Design Methods By Jeffrey L Whitten & Lonnie D Bentley , Analysis & Design of Information Systems By James A. Senn, System Analysis & Design By Elias M. Awad, Modern System Analysis & Design By Jeffrey A. Hoffer, Joey F.George & Joseph S. Valacich Vinay Arora CSED
- 3. Top Down Design In principle, top-down design involves starting at the uppermost components in the hierarchy and working down the hierarchy level by level. In practice, large systems design is never truly top-down. Some branches are designed before others. Designers reuse experience (and sometimes components) during the design process. Each function the system will perform is first identified and then developed in greater detail. This is termed as Stepwise Refinement. Vinay Arora CSED
- 4. Top Down Structure Vinay Arora CSED
- 5. Top Down Structure System level Sub-system level Vinay Arora CSED
- 6. Update File as Main Procedure & Various Sub Procedures Vinay Arora CSED
- 7. Coupling A measure of the strength of the inter-connections between system components. Loose coupling means component changes are unlikely to affect other components. Shared variables or control information exchange lead to tight coupling. Loose coupling can be achieved by component communication via parameters or message passing. Vinay Arora CSED
- 8. Coupling Vinay Arora CSED
- 9. Tight Coupling Module A Module B Module C Module D Shared data area Vinay Arora CSED
- 10. Loose Coupling Module A A’s data Module B Module C B’s data C’s data Module D D’s data Vinay Arora CSED
- 11. Cohesion A measure of how well a component “fits together”. A component should implement a single logical entity or function. Cohesion is a desirable design component attribute as when a change has to be made, it is localized in a single cohesive component. Various levels of cohesion have been identified. Vinay Arora CSED
- 12. Coupling & Cohesion Vinay Arora CSED
- 13. Span of Control Span of control is the term now used more commonly in business management, particularly human resource management. Span of control refers to the number of subordinates a supervisor has. In software design span of control is the total count of sub modules as controlled by a main module. Vinay Arora CSED
- 14. Shared Module Vinay Arora CSED
- 15. Reference List 1. System Analysis and Design Methods By Jeffrey L Whitten & Lonnie D Bentley 2. Analysis & Design of Information Systems By James A. Senn 3. System Analysis & Design By Elias M. Awad 4. Modern System Analysis & Design By Jeffrey A. Hoffer, Joey F.George & Joseph S. Valacich etc……. Vinay Arora CSED
- 16. Thnx… Vinay Arora CSED