HPE NonStop (formerly Tandem) represents a line of fault-tolerant, high-availability servers designed for 24/7, zero-downtime operations. Originally created by Tandem Computers in 1974, the architecture is now owned by Hewlett Packard Enterprise (HPE) and supports mission-critical workloads like banking and finance. 

Key Aspects of HPE NonStop (Tandem):

• Continuous Availability: Designed to eliminate single points of failure with 100% fault tolerance.
• Architecture: Initially used a proprietary Tandem T/16 design; modern systems are based on HPE Integrity/x86 architectures.
• Operating System: Traditionally runs the Guardian OS, which handles the system’s specialized, continuous processing capabilities.
• Evolution: Founded by James Treybig in 1974, Tandem was acquired by Compaq in 1997, which then merged with HP in 2002.
• Applications: Ideal for transactional applications requiring strict data integrity and real-time processing.
• Modern Platforms: Current systems include HPE NonStop Compute NS9 X5 and NS5 X5. 

The systems are still widely used today for mission-critical applications that cannot afford to be offline. 

HPE NonStop (formerly Tandem) represents a line of fault-tolerant, high-availability servers.