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
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CSED

5. Top Down Structure
System level
Sub-system
level
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CSED

6. Update File as Main Procedure & Various Sub
Procedures
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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
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CSED

9. Tight Coupling
Module A Module B
Module C Module D
Shared data
area
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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
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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
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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