Which is not a search engine?

A search engine is a software system designed to perform web searches, systematically looking for specific information on the World Wide Web based on a user's query. Windows is the correct answer because it is an operating system developed by Microsoft. An operating system manages computer hardware and software resources, providing a platform for applications to run, but it is not a tool for searching the internet for information.

• Google is incorrect; it is the most widely used search engine globally, known for its comprehensive indexing and advanced search algorithms.
• Bing is incorrect; it is a prominent search engine operated by Microsoft, offering various search services.
• Yahoo is also incorrect; it is a well-known web portal that includes a search engine, historically a major player in web search. All three are indeed search engines.