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Software > OpenVMS Systems > Ask the Wizard ![]() HP OpenVMS Systemsask the wizard |
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The Question is: Mr. Wizard, What is a 'template' device? The Answer is : A template device is a device that is not directly used, but serves as the basis for the creation of cloned device -- assigning a channel to a template device will result in the creation of a device cloned from the template, and a channel to the clone will be returned to the caller. For example, Ethernet devices (eg: EW, etc) are template devices, and each active Ethernet protocol type gets its own cloned device -- the basic characteristics of the device are stored in the template, and is replicated for each Ethernet protocol currently in use. LAT terminals (eg: LT devices) also use template devices, and thus each connection into the network drivers gets its own device data structures. And in the specific case of the LAT drivers, there will be an Ethernet cloned device layered underneath the LT device that is specific to the LAT Ethernet protocol code (60-04) -- this permits an interactive user of LAT to have something that looks and works like a terminal, but that is implemented using a network device driver. The template device permits an easy way to store the information that is unique to each device and to each class of device, and to store a set of basic device attributes in a common area, and can permit the system to be configured with the minimum number of device-related data structures around.
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