How is Software Development guided?

The software development process is almost invariably guided by some systematic software development method (SDM). Referred to by a number of terms, including process models, development guidelines, and systems development life cycle models (SDLC), software development methods nevertheless generally include the same development phases:

The existing system is evaluated and its deficiencies identified, usually through interviewing system users and support personnel.

The new system requirements are defined. In particular, the deficiencies in the existing system must be addressed with specific proposals for improvement.
The proposed system is designed. Plans are laid out concerning the physical construction, hardware, operating systems, programming, communications, and security issues.

The new system is developed. The new components and programs must be obtained and installed. Users of the system must be trained in its use, and all aspects of performance must be tested. If necessary, adjustments must be made at this stage.
The system is put into use. This can be done in various ways. The new system can phased in, according to application or location, and the old system gradually replaced. In some cases, it may be more cost-effective to shut down the old system and implement the new system all at once.

Once the new system is up and running for awhile, it should be exhaustively evaluated. Maintenance must be kept up rigorously at all times. Users of the system should be kept up-to-date concerning the latest modifications and procedures.