SOFTWARE DEVELOPMENT LIFE CYCLE

Software Elements Analysis: The most important task in creating a software product is extracting the requirements. Customers typically know what they want, but not what software should do, while incomplete, ambiguous or contradictory requirements are recognized by skilled and experienced software engineers. Frequently demonstrating live code may help reduce the risk that the requirements are incorrect.
Requirements (Requirements Specification): There is the task of precisely describing the software to be written, possibly in a rigorous way. In practice, most successful requirements are written to understand and fine-tune applications that were already well-developed, although safety-critical software systems are often carefully specified prior to application development. Requirements are most important for external interfaces that must remain stable.
Software architecture: The architecture of a software system refers to an abstract representation of that system. Architecture is concerned with making sure the software system will meet the requirements of the product, as well as ensuring that future requirements can be addressed. The architecture step also addresses interfaces between the software system and other software products, as well as the underlying hardware or the host operating system.
Implementation (or coding): Reducing a design to code may be the most obvious part of the software engineering job, but it is not necessarily the largest portion.
Testing: Testing of parts of software, especially where code by two different engineers must work together, falls to the software engineer.
Documentation: An important (and often overlooked) task is documenting the internal design of software for the purpose of future maintenance and enhancement. Documentation is most important for external interfaces.
Software Training and Support: A large percentage of software projects fail because the developers fail to realize that it doesn't matter how much time and planning a development team puts into creating software if nobody in an organization ends up using it. People are occasionally resistant to change and avoid venturing into an unfamiliar area, so as a part of the deployment phase, its very important to have training classes for the most enthusiastic software users (build excitement and confidence), shifting the training towards the neutral users intermixed with the avid supporters, and finally incorporate the rest of the organization into adopting the new software. Users will have lots of questions and software problems which leads to the next phase of software.
Maintenance: Maintaining and enhancing software to cope with newly discovered problems or new requirements can take far more time than the initial development of the software. Not only may it be necessary to add code that does not fit the original design but just determining how software works at some point after it is completed may require significant effort by a software engineer. About ⅔ of all software engineering work is maintenance, but this statistic can be misleading. A small part of that is fixing bugs. Most maintenance is extending systems to do new things, which in many ways can be considered new work. In comparison, about ⅔ of all civil engineering, architecture, and construction work is maintenance in a similar way.