This document provides an introduction to the Software Development Life Cycle (SDLC) process for a software engineering course. It describes the typical stages of the SDLC, including planning, requirements analysis, design, development, testing, deployment, and maintenance. It then focuses on explaining the Waterfall model as one of the most popular SDLC models, outlining its sequential phases and noting that it is best suited for projects with well-defined requirements and stable scope.

1. Introduction to Software Engineering
(CSC291)
Instructor
Humaira Afzal
Lecturer
humairaafzal@ciitlahore.edu.pk
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2. SDLC
SDLC, Software Development Life Cycle is a process
used by software industry to design, develop and test
high quality software.
The SDLC aims to produce a high quality software
that meets or exceeds customer expectations,
reaches completion within times and cost estimates.
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3. SDLC
A typical Software Development life cycle consists of the
following stages:
1. Planning and Requirement Analysis
2. Defining Requirements
3. Designing the product architecture
4. Building or Developing the Product
5. Testing the Product
6. Deployment in the Market and Maintenance
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Software Process/SDLC Models
“A software process model is an abstract representation of a software
(i.e. a roadmap)”
Following are the most important and popular SDLC models followed in
the industry:
• Waterfall Model
• Iterative Model
• Spiral Model
• V-Model
• Incremental Model
The other related methodologies are Agile Model, RAD Model – Rapid
Application Development and Prototyping Models.

6. Waterfall Model
• The first published model of the software development
process.
• Because of the cascade from one phase to another, this
model is known as ‘Waterfall Model’.
• It is also referred to as linear-sequential life cycle model.
• It is very simple to understand and use.
• Each phase must be completed before the next phase can
begin and there is no overlapping in the phases.
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7. Waterfall Model
The sequential phases in Waterfall model are:
Requirement Gathering and analysis: All possible requirements of the
system to be developed are captured in this phase and documented in a
requirement specification doc.
• System’s services
• Constraints
• Goals
System Design: The requirement specifications from first phase are studied
in this phase and system design is prepared. System Design helps in
specifying hardware and system requirements and also helps in defining
overall system architecture.
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8. Waterfall Model
Implementation and unit testing: With inputs from system design, the
system is first developed in small programs called units, which are
integrated in the next phase. Each unit is developed and tested for its
functionality which is referred to as Unit Testing.
Integration and Testing: All the units developed in the implementation
phase are integrated into a system after testing of each unit. Post
integration the entire system is tested for any faults and failures.
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9. Waterfall Model
Deployment of system: Once the functional and non functional testing is
done, the product is deployed in the customer environment or released
into the market.
Maintenance: There are some issues which come up in the client
environment. To fix those issues patches are released. Also to enhance the
product some better versions are released. Maintenance is done to
deliver these changes in the customer environment.
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10. Waterfall Model
All these phases are cascaded to each other in which progress
is seen as flowing steadily downwards (like a waterfall)
through the phases.
The next phase is started only after the defined set of goals
are achieved for previous phase and it is signed off, so the
name "Waterfall Model". In this model phases do not overlap.
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12. Waterfall Model Application
Every software developed is different and requires a suitable SDLC
approach to be followed based on the internal and external factors.
Some situations where the use of Waterfall model is most
appropriate are:
• Requirements are very well documented, clear and fixed
• Product definition is stable
• Technology is understood
• There are no ambiguous requirements
• The project is short
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13. Waterfall Model Advantages
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• Documentation is produced at each phase
• Simple and easy to understand and use.
• Phases are processed and completed one at a time.
• Works well for smaller projects where requirements are very well understood.
• Clearly defined stages.
• Well understood milestones.
• Easy to arrange tasks.
• Process and results are well documented.

14. Waterfall Model disadvantages
• Not a good model for complex and object-oriented projects.
• Poor model for long and ongoing projects.
• Risk and uncertainty is high with this process model.
• It is difficult to measure progress within stages.
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• Difficult to accommodate changing customer requirements after
the process is underway
• Appropriate only when the requirements are well-understood

15. Challenges
• In practice , Development stages overlap..
• Software process is not a simple linear model..
• In case of error and the need for new functionality..
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