Output device definitions may specify more than the output destination - they may also contain initialisation information. This means that when your application selects a device for output, it not only notifies the OSDI which component of the Device Group is to be used, but it also passes some information to define the way output is to be handled.
For example, you may have a printer on a till capable of printing in various character sizes. DP4 allows you to define devices in such a way that the definition encapsulates not only the destination of output (the till printer) but also output data characteristics (in this case character size). One output device may thus be diversified (you may define three printers, all printing at the till printer but all at different character sizes).
DP4 uses the concept of CODs (Component Output Devices) to define generic output device types. A COD definition may include a set of parameters where each individual parameter can only take one member of a defined range of values. The selection of one set of specific parameter values from the defined range of all possible values produces a POD (parameterised output device). In this way a single COD definition may give rise to one or more PODs. DP4 applications always view devices as PODs.
More information on CODS and PODS can be found in CODs and PODs.