Editing NonStop (server computers) (section)

==Software==
NonStop OS is a [[message passing|message-based]] operating system designed for fault tolerance. It works with process pairs and ensures that backup processes on redundant CPUs take over in case of a process or CPU failure. Data integrity is maintained during those takeovers; no transactions or data are lost or corrupted.

The operating system as a whole is branded NonStop OS and includes the Guardian layer, which is a low-level component of the operating system and the Open System Services (OSS) personality which runs atop this layer, which implements a Unix-like interface for other components of the OS to use.

The operating system and application are both designed to support the fault tolerant hardware. The operating system continually monitors the status of all components, switching control as necessary to maintain operations. There are also features designed into the software that allow programs to be written as continuously available programs. That is accomplished using a pair of processes where one process performs all the primary processing and the other serves as a "hot backup", receiving updates to data whenever the primary reaches a critical point in processing. Should the primary stop, the backup steps in to resume execution using the current transaction.<ref>{{cite book |title=HP NonStop Server Security: A Practical Handbook |date=6 October 2003 |publisher=Digital Press |isbn=978-1555583149}}</ref>

The systems support [[relational database management system]]s like [[NonStop SQL]] and hierarchical databases such as [[Enscribe]].

Languages supported include [[Java (programming language)|Java]],<ref name=":0">{{cite web |title=Engineered for the highest availability – HPE NonStop family of systems brochure |url=https://www.hpe.com/psnow/doc/4aa4-2988enw.pdf?jumpid=in_pdfviewer-psnow |page=10}}</ref> [[C (programming language)|C]], [[C++]],<ref name=":0"/> [[COBOL]], SCOBOL (Screen COBOL), [[Transaction Application Language]] (TAL), etc. It uses the scripting and job control language [[TACL (programming language)|TACL]] (Tandem Advanced Command Language), and is written in TAL and C.