Editing Legacy system (section)

==Alternative view==
There is an alternate favorable opinion—growing since the end of the Dotcom bubble in 1999—that legacy systems are simply computer systems in working use:

{{Blockquote|"[[Legacy code]]" often differs from its suggested alternative by actually working and scaling.|[[q:Bjarne Stroustrup|Bjarne Stroustrup, creator of C++]]}}

IT analysts estimate that the cost of replacing [[business logic]] is about five times that of reuse,<ref>{{Cite web |title=Cost Considerations For A Mainframe to Cloud Migration Project |url=https://kumaran.com/blogs/cost-considerations-for-a-mainframe-migration-project/ |website=Kumaran Systems|date=24 March 2023 }}</ref> even discounting the risk of system failures and security breaches. Ideally, businesses would never have to [[Rewrite (programming)|rewrite]] most core business logic: ''debits = credits'' is a perennial requirement.

The IT industry is responding with "legacy modernization" and "legacy transformation": refurbishing existing business logic with new user interfaces, sometimes using [[screen scraping]] and service-enabled access through [[web service]]s. These techniques allow organizations to understand their existing code assets (using discovery tools), provide new user and application interfaces to existing code, improve workflow, contain costs, minimize risk, and enjoy classic qualities of service (near 100% uptime, security, scalability, etc.).<ref>{{Cite web |last=Comella-Dorda |first=Santiago |date=2000-04-01 |title=A Survey of Legacy System Modernization Approaches |url=https://resources.sei.cmu.edu/asset_files/TechnicalNote/2000_004_001_13673.pdf |website=SEI Digital Library}}</ref>

This trend also invites reflection on what makes legacy systems so durable. Technologists are relearning the importance of sound [[Computer architecture|architecture]] from the start, to avoid costly and risky rewrites. The most common legacy systems tend to be those which embraced well-known IT architectural principles, with careful planning and strict methodology during implementation. Poorly designed systems often don't last, both because they wear out and because their inherent faults invite replacement. Thus, many organizations are rediscovering the value of both their legacy systems and the theoretical underpinnings of those systems.