Discuss the essential phases of system development life cycleand compare the sdlc waterfall model with the spiral model?

The System Development Life Cycle (SDLC) consists of essential phases: requirements gathering, system design, implementation, testing, deployment, and maintenance. The Waterfall model follows a linear, sequential approach where each phase must be completed before moving to the next, making it easier to manage but less flexible to changes. In contrast, the Spiral model incorporates iterative cycles, allowing for continuous refinement and risk assessment throughout the development process, which makes it more adaptable to evolving requirements. While the Waterfall model is suitable for well-defined projects, the Spiral model is better for complex projects where user feedback and risk management are critical.