Release 17.0, Stratus offers support for distributing OpenVOS on a DVD or by downloading a release file. Software installations may be done by the Stratus Field Engineer or by the customer's system administrator. Interface The command-line interface is the main, and most powerful, user interface for a VOS system. Users may be locked into "form" based sub-system by command macro scripts if required, although a skilled user would be able to break out of this and get command-line access. (It is, in fact, possible for a Stratus system administrator to set up a user's account such that an attempt to break out of FMS—the Stratus Forms Management System—to the command line results in the user being logged out.) Command macros and programs can be invoked with an argument to display a form listing all the available parameters, which the user can navigate using the "tab" key. Each parameter is generally restricted to control what the user can input. This includes lists of valid values, numeric-only, text-only, etc. Parameters can also be hidden using a "secret" tag, or made mandatory. All commands in VOS are defined in full with underbars to separate words. For example, changes the working directory. The VOS help system uses this convention to assist users who are looking for a subset of possible commands; for instance, those referring to "change" are found by . Users may customize their command interface by means of a file that contains abbreviations for commands. Command abbreviations are conventionally named after the first letters of the command they represent, so may be expanded to . Applications System applications VOS is used on Continuum and ftServer systems, both of which are designed to be highly fault-tolerant. As such, these systems are typically used in safety-critical or mission-critical applications, typically banks, hospitals, telecommunications and transaction processing companies. Communications VOS supports the following protocols TCP/IP X.25 SNA SDLC/QLLC Async Bisync LAPB Poll/Select RJE/HASP ALC/SLC Visa, S.W.I.F.T., NASDAQ, FAS, CHIPS, AMEX MQ Series Older versions of VOS implemented a non-OSI standard TCP/IP known as OS TCP/IP (Operating System TCP/IP.) VOS since version 14.x has implemented OSI-compliant Streams-TCP. Older applications using OS TCP/IP have to be ported in order to use STCP. This can mean a loss of functionality as OS TCP/IP supported several functions that are not OSI-compliant and have therefore been abandoned. The ftServer hardware that V Series runs on only supports TCP/IP and X.25