Perhaps one of the most confusing things which MOSES does is dealing with devices. By device, we mean either a physical piece of hardware such as a printer, pen plotter, terminal screen, or logical device such as a file. In MOSES there are two concepts: a channel and a logical device. Basically, channels can be thought of as either files or as directly connected physical devices. Logical devices are different classes of output which are "connected" to a channel. As data is written to a logical device, it is formatted according to a set of instructions collectively called a style. In the following pages, each of these concepts will be defined in detail. For most of the things defining device attributes, the units required are points. A point is 1/72 of an inch or .3527 mm. The exception to the above rule is when one defines the "pitch" of a fixed pitch font which is defined in characters per inch.