(SEM VI) THEORY EXAMINATION 2017-18 SOFTWARE ENGINEERING

Software Engineering (NCS602 / ECS602)

Complete Section-Wise Explanation – B.Tech Semester VI

Introduction to the Subject

Software Engineering is the systematic approach to the development, operation, maintenance, and retirement of software systems. The subject focuses on building high-quality, reliable, maintainable, and cost-effective software using well-defined processes, tools, and techniques.

This subject helps students understand:

Software development life cycle (SDLC)

Software process models

Requirement analysis and SRS

Software design principles

Testing strategies

Cost estimation and quality models

Software maintenance and risk management

The question paper is divided into three sections: A, B, and C, all of which must be attempted as per instructions.

SECTION A – Short Answer Questions

(2 × 10 = 20 marks)

Section A checks your basic conceptual clarity. Answers should be short but meaningful, usually 2–3 lines, and technically correct.

Explanation of Section A Questions

Software Crisis
Software crisis refers to the difficulties faced in developing large software systems, such as cost overruns, delayed delivery, low quality, and poor maintainability. It led to the emergence of software engineering as a discipline.

Software Quality Attributes
Software quality attributes include reliability, efficiency, usability, maintainability, portability, security, and correctness. These attributes determine how well software meets user and system requirements.

Verification vs Validation
Verification checks whether the software is built correctly according to specifications, while validation checks whether the right software is built to satisfy user needs.

Decision Tree
A decision tree is a graphical representation of decisions and their possible consequences. It is often used in testing and decision analysis.

Principles of Software Design
Software design principles focus on modularity, abstraction, information hiding, cohesion, and low coupling to make software easy to understand and maintain.

Pseudo Code and Algorithm
Pseudo code is an informal, English-like description of program logic, while an algorithm is a formal step-by-step procedure to solve a problem.

Code Inspection
Code inspection is a static verification technique where code is reviewed manually to detect defects without executing the program.

Stub and Driver
Stubs are dummy modules used during top-down testing, while drivers are dummy calling programs used during bottom-up testing.

CASE Tools
CASE (Computer-Aided Software Engineering) tools support activities such as analysis, design, coding, testing, and maintenance of software.

Adaptive and Corrective Maintenance
Corrective maintenance fixes defects found after delivery, while adaptive maintenance modifies software to work in a changed environment.

SECTION B – Descriptive & Analytical Questions

(Attempt any three, 10 × 3 = 30 marks)

Section B requires detailed explanations written in paragraph form, supported with diagrams, examples, and comparisons where applicable.

Spiral Model – Advantages and Disadvantages

The Spiral Model combines iterative development with risk analysis. Each loop of the spiral includes planning, risk analysis, engineering, and evaluation.
Its advantages include early risk identification, flexibility, and suitability for large projects.
Disadvantages include high cost, complexity, and the need for skilled risk assessment.

CMM Model and Comparison with ISO

The Capability Maturity Model (CMM) measures the maturity of software development processes across five levels: Initial, Repeatable, Defined, Managed, and Optimizing.
ISO focuses on quality standards and documentation, while CMM emphasizes continuous process improvement and maturity.

Methods of Verification

Verification ensures correctness without executing code.
Common methods include reviews, walkthroughs, inspections, and static analysis. These methods help detect errors early, reducing cost and rework.

Structure Chart and Its Basic Blocks

A structure chart represents the hierarchical organization of software modules.
Basic blocks include sequence, selection, and iteration.
It helps in understanding module relationships, data flow, and control flow.

Cost Analysis and COCOMO Model

Cost analysis estimates effort, time, and cost of software development.

The COCOMO (Constructive Cost Model) estimates effort based on software size and development mode (organic, semi-detached, embedded). It helps in project planning and budgeting.

SECTION C – Long Answer Questions

(5 × 10 = 50 marks)

Section C has the highest weightage and requires well-structured, in-depth answers.

Question 3

Phases of Software Development Life Cycle (SDLC)

SDLC includes requirement analysis, system design, implementation, testing, deployment, and maintenance. Each phase plays a vital role in ensuring software quality and user satisfaction.

OR

Iterative Enhancement Model

This model develops software in small increments. Each iteration adds functionality based on user feedback.
Advantages include early delivery and flexibility, while disadvantages include management complexity.

Question 4

Data Flow Diagram (DFD)

A DFD represents data flow within a system.
Basic components include processes, data stores, data flows, and external entities.
DFDs help in understanding system requirements visually.

OR

Software Requirement Specification (SRS)

SRS is a formal document describing software requirements.
A good SRS should be correct, complete, consistent, unambiguous, verifiable, and modifiable.

Question 5

Objectives and Approaches of Software Design

The objective of software design is to convert requirements into a workable solution.
Approaches include top-down design, bottom-up design, and structured design.

OR

Cyclomatic Complexity

Cyclomatic complexity measures program complexity based on control flow.
It can be calculated using control flow graph edges and nodes, number of decision points, or regions. It helps in testing and maintainability analysis.

Question 6

Regression Testing and Test Case Prioritization

Regression testing ensures that changes do not introduce new defects.
Test case prioritization orders test cases based on importance, risk, or recent changes to improve efficiency.

OR

Integration Testing

Integration testing checks interactions between modules.
Approaches include top-down, bottom-up, and sandwich testing.

Question 7

Software Configuration Management (SCM)

SCM manages changes in software artifacts.
Activities include configuration identification, version control, change control, status accounting, and audits.

OR

Software Risk Analysis and Management

Risk management identifies, analyzes, and mitigates project risks.
It involves risk identification, risk assessment, risk prioritization, and risk control to ensure project success.