System Development Life Cycle (SDLC)
SDLC is a structured framework that defines the tasks and phases involved in developing an information system from initial planning through maintenance. It provides a systematic approach to building quality systems.
Definition
The System Development Life Cycle (SDLC) is a well-defined, organized process consisting of distinct phases that guide the development of an information system. Each phase has specific deliverables and objectives that must be completed before moving to the next phase.
Phases of SDLC
Phase A: Planning (System Investigation)
- This is the first phase where the problem or need is identified
- A feasibility study is conducted to determine whether the project is technically, economically, and operationally viable
- The scope, objectives, and constraints of the project are defined
- Resources, timeline, and budget are estimated
- Output: Feasibility Report
Phase B: System Analysis
- In this phase, the current system is studied in detail to understand its strengths and weaknesses
- Requirements gathering is done through interviews, questionnaires, observation, and document analysis
- Analysts determine what the system must do (functional and non-functional requirements)
- Data flow diagrams (DFDs), use cases, and ER diagrams are prepared
- Output: System Requirements Specification (SRS)
Phase C: System Design
- This phase answers how the system will work
- Logical design defines the structure — inputs, outputs, processes, databases
- Physical design specifies hardware, software, network, and user interface
- Two levels:
- High-Level Design (HLD): Overall system architecture
- Low-Level Design (LLD): Detailed module-level design
- Output: Design Document/Specification
Phase D: Implementation (Coding/Development)
- The actual source code is written based on the design documents
- Programmers use appropriate programming languages and tools
- The system is built module by module
- Coding standards and guidelines are followed
- Output: Working Software Modules
Phase E: Testing
- The developed system is tested for errors, bugs, and defects
- Types of testing performed:
- Unit Testing — individual modules tested
- Integration Testing — modules tested together
- System Testing — entire system tested as a whole
- Acceptance Testing — tested by end users
- Ensures the system meets the specified requirements
- Output: Test Reports and Bug-free System
Phase F: Deployment (Installation)
- The system is delivered and installed in the real environment
- Users are trained to use the new system
- Conversion strategies used:
- Direct changeover — old system replaced immediately
- Parallel conversion — both systems run simultaneously
- Phased conversion — system introduced in parts
- Pilot conversion — introduced at one location first
- Output: Operational System
Phase G: Maintenance
- This is the longest phase of SDLC
- The system is monitored, updated, and improved after deployment
- Types of maintenance:
- Corrective — fixing discovered bugs
- Adaptive — adapting to new environment changes
- Perfective — enhancing performance or adding features
- Preventive — preventing future problems
- Output: Updated and Improved System
Conclusion
The SDLC provides a disciplined and systematic approach to system development. Each phase builds upon the previous one, ensuring that the final system is well-planned, properly designed, thoroughly tested, and easy to maintain. Following SDLC reduces project risks, controls costs, and delivers quality software.