Coding best practices are a set of informal rules that the software development community employs to help improve software quality.Many computer programs remain in use for long periods of time, so any rules need to facilitate both initial development and subsequent maintenance and enhancement by people other than the original authors. In ninety-ninety rule, Tom Cargill is credited with an explanation as to why programming projects often run late: "The first 90% of the code accounts for the first 90% of the development time.