System development life cycle (SDLC)

Basic Concept of SDLC – System Development Life Cycle

A successful Organizations use a standard set of steps, called a systems development methodology, to develop and support their information systems. Like many processes, the development of information systems often follows a life cycle.
For example, a commercial product, such as a

• Nike sneaker or
• a Honda car,

follows a life cycle:

1. It is created,
2. tested, and
3. introduced to the market.
4. Its sales increase,
5. peak, and
6. decline.
7. Finally, the product is removed from the market and
8. is replaced by something else.

The systems development life cycle (SDLC) is a common methodology for systems development in many organizations.
It marks the phases or steps of information systems development:

• Someone has an idea for an information system and what it should do.
• The organization that will use the system decides to devote the necessary resources to acquiring it.
• A careful study is done of how the organization currently handles the work the system will support.
• Professionals develop a strategy for designing the new system,
• which is then either built or purchased.
• Once complete, the system is installed in the organization, and
• after proper training, the users begin to incorporate the new system into their daily work.

Every organization uses a slightly different life-cycle model to model these steps, with anywhere from three to almost twenty identifiable phases.

A successful System Development Life Cycle (SDLC) should result in an astounding system that meets client desires, achieves expectations within time and cost assessments, and works viably and productively in the current and planned Information Technology framework. 

System Development Life Cycle (SDLC) is an applied model which incorporates strategies and methods for creating or modifying systems throughout their life cycles. 

SDLC is utilized by examiners to build up a data system. SDLC incorporates the accompanying exercises −

• requirements
• design
• implementation
• testing
• deployment
• operations
• maintenance

Basic Four phases of SDLC

The system development life cycle structure gives a grouping of exercises to system designers and engineers to take after. It comprises of an arrangement of steps or stages in which each period of the SDLC utilizes the aftereffects of the past one. 

The SDLC holds fast to critical stages that are basic for engineers, for example, planning, analysis, design, and implementation—and are clarified in the area beneath. This incorporates assessment of the presently utilized system, data gathering, feasibilty studies, and demand endorsement. Various SDLC models have been made, including waterfall, fountain, spiral, build and fix, rapid prototyping, incremental, synchronize, and stabilize. The oldest of these, and the best known, is the waterfall model, a succession of stages in which the yield of each stage turns into the contribution for the next. These stages can be described and partitioned up in various ways, including the following:

1.  planning and selection,
2.  analysis,
3.  design, and
4.  implementation and operation (see Figure 1).

figure: 1

Feasibility Study or Planning 

1. Characterize the issue and extent of existing system. 
2. Diagram the new system and decide its goals. 
3. Affirm venture feasibility and deliver the task Schedule. 
4. Amid this stage, dangers, imperatives, combination and security of system are likewise considered. 
5. A feasibility report for the whole venture is made toward the finish of this stage. 

Analysis and Specification 

1. Assemble, examine, and approve the data. 
2. Characterize the prerequisites and models for new system. 
3. Assess the options and organize the prerequisites. 
4. Analyze the data needs of end-client and upgrades the system objective. 
5. A Software Requirement Specification (SRS) archive, which determines the product, equipment, useful, and organize prerequisites of the system is set up toward the finish of this stage. 

System Design 

1. Incorporates the design of utilization, organize, databases, UIs, and system interfaces. 
2. Change the SRS report into coherent structure, which contains definite and finish set of specifications that can be executed in a programming dialect. 
3. Make a possibility, preparing, maintenance, and activity design. 
4. Survey the proposed design. Guarantee that the last design must meet the prerequisites expressed in SRS record. 
5. At long last, set up a design record which will be utilized amid next stages. 

Implementation 

1. Execute the design into source code through coding. 
2. Join every one of the modules together into preparing condition that recognizes mistakes and imperfections. 
3. A test report which contains mistakes is set up through test arrange for that incorporates test related undertakings, for example, experiment age, testing criteria, and asset allotment for testing. 
4. Incorporate the data system into its condition and introduce the new system. 

Maintenance/Support 

1. Incorporate every one of the exercises, for example, telephone support or physical on location support for clients that is required once the system is introducing. 
2. Execute the progressions that product may experience over some undefined time frame, or actualize any new necessities after the product is sent at the client area. 
3. It additionally incorporates handling the leftover blunders and resolve any issues that may exist in the system even after the testing stage. 
4. Maintenance and support might be required for a more extended time for vast systems and for a brief span for littler systems.

Although any life cycle appears at first glance to be a sequentially ordered set of phases, it actually is not. The specific steps and their sequence are meant to be adapted as required for a project. For example,

• in any given SDLC phase, the project can return to an earlier phase, if necessary.
• Similarly, if a commercial product does not perform well just after its introduction, it may be temporarily removed from the market and improved before being reintroduced.
• In the systems development life cycle, it is also possible to complete some activities in one phase in parallel with some activities of another phase.
• Sometimes the life cycle is iterative; that is, phases are repeated as required until an acceptable system is found.
• Some systems analysts consider the life cycle to be a spiral, in which we constantly cycle through the phases at different levels of detail, as illustrated in Figure 2.
• The circular nature of the life-cycle diagram in Figure 2 illustrates how the end of the useful life of one system

figure: 2

leads to the beginning of another project that will replace the existing system altogether. However conceived, the systems development life cycle used in an organization is an orderly set of activities conducted and planned for each development project. The skills required of a systems analyst apply to all lifecycle models

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