Part 1 of Essay
During the 1950’s, era of computing, computer programs were created using ad hoc software development approach; each system a unique, custom-built intellectual product. In their book, & Design, Edward Yourdon and Carl Argila state “There was no concept of reusability, interchangeability of parts, or for that matter, form ....

Part 2 of Essay
.... the 1970’s, a new approach was developed. Tom Demarco, is his book, Structured Analysis and System Specification, introduced model-based software engineering. Demarco thought that complex software systems should be built like any large, complex engineering system, by first building working paper models of the system before committing the resources for implementation. This allowed the user to visualize the future system. Most modern approaches have integrated some form of Demarco’s philosophy. The variation in ....