System development is the process of defining, designing, testing and implementing a software application. This includes the internal development of customized systems as well as the acquisition of software developed by third parties. A system development project includes all the activities from the time a potential requirement has been identified until the system has been fully implemented.


The systems development life cycle, or SDLC, is the process of creating systems and the models used to develop these systems. A typical SDLC includes a number of different phases, such as requirements analysis, software design, software coding, testing and debugging, installation and maintenance. This life cycle is implemented using a software development process. There are a number of models of software development, each with a somewhat different approach to implementing the various phases of the life cycle.


The waterfall model of software development follows a very sequential design process. It is also referred to as a linear-sequence life-cycle model. In this model, progress is seen as flowing downwards through various phases, like a waterfall. The phases include initiation and conception, requirements analysis, software design, construction (or coding), testing and debugging, installation and maintenance. The basic premise of the waterfall model is that you only move to the next phase when the preceding phase is completed successfully. This approach works well for projects that are relatively simple.

The V-model is an extension of the waterfall model. Instead of moving down in a linear way, the process steps go upwards after the coding phase to form a V shape. This shape demonstrates the relationship between each early phase of development and the associated testing phase. In this approach, testing procedures are developed early in the life cycle, even before any coding is done. Testing holds a much greater emphasis here compared to the waterfall model.

The iterative and incremental model employs a cyclical approach. It starts with an initial planning phase and ends with deployment, with cyclic interactions taking place in between. The approach is incremental since it divides the functionality into small increments, which are developed and tested over one or more iterations.

The software prototyping model relies on creating and testing prototypes of software applications. A prototype is a simple, incomplete version of the software being developed. An initial prototype is developed that meets some of the very basic requirements but lacks many of the details. The initial prototype is tested and reviewed, and the feedback is used to improve the prototype.

The spiral model combines elements of various other models, the waterfall and prototyping models in particular. It is typically used for large and complicated projects. The approach starts with a small prototype, which is followed by a short version of the waterfall process. This is mostly to gather requirements. The first prototype is reviewed, and in subsequent loops, additional requirements are identified, and a more detailed design is developed and implemented.