The primary use of a mainframe computer is to handle large volumes of transaction processing and data processing tasks efficiently. These powerful machines are often used by large organizations for critical applications, such as enterprise resource planning (ERP), database management, and bulk data analytics. Mainframes are known for their reliability, scalability, and ability to support numerous users simultaneously without compromising performance. Their robustness makes them essential in industries such as finance, healthcare, and government for tasks that require high availability and security.