System Development Life Cycle (SDLC) is the overall process of developing information systems through a multistep process from investigation of initial requirements through analysis, design, implementation and maintenance.

There are many different models and methodologies, but each generally consists of a series of defined steps or stages.

RUP is one of the different types of SDLC.  The Rational Unified Process is a very modern, very forward looking iterative type of the SDLC. 

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