Short Notes

(a) Software Reuse

Software reuse means using existing software assets—such as components, libraries, frameworks, designs or services—in a new system instead of developing everything from scratch.

Benefits

• Reduces development time and cost.
• Improves reliability when proven components are reused.
• Promotes standardization.
• Reduces duplicated effort.

Example

A developer may reuse an existing authentication library rather than implementing password hashing and session management from the beginning.

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(b) Capability Maturity Model (CMM)

The Capability Maturity Model is a framework for assessing and improving the maturity of an organization's software development process.

Five maturity levels

1. Initial — process is ad hoc and unpredictable.
2. Repeatable — basic project-management practices are established.
3. Defined — processes are documented and standardized across the organization.
4. Managed — processes are measured and controlled quantitatively.
5. Optimizing — continuous process improvement is emphasized.

CMM helps organizations make their software processes more disciplined, measurable and predictable.

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(c) Functional and Non-functional Requirements

Functional requirements

Describe what the system must do—its services, behaviors and responses.

Example: "The ATM shall allow a customer to withdraw cash after successful authentication."

Non-functional requirements

Describe how well the system must operate or constraints under which it must operate.

Examples: performance, security, reliability, usability and availability.

Functional	Non-functional
Specifies system behavior/services	Specifies qualities and constraints
Example: process a withdrawal	Example: respond within 2 seconds

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(d) Software Re-engineering

Software re-engineering is the systematic examination and transformation of an existing software system to improve its maintainability, structure, performance or technology while preserving useful functionality.

Typical activities

• Inventory analysis: identify systems/components that need attention.
• Document restructuring: improve missing or outdated documentation.
• Reverse engineering: recover higher-level design/knowledge from existing code.
• Code restructuring: improve source code structure without changing intended behavior.
• Data restructuring: reorganize or migrate data.
• Forward engineering: rebuild or modernize the system using recovered knowledge.

Benefits

• Extends software life.
• Reduces maintenance difficulty.
• Preserves valuable business functionality.
• Can be cheaper and less risky than replacing a mature system completely.