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SLIDES fully supports the 3-D graphics capabilities of the CORE system, and for the LINE, MARK, and MOVE commands, the 4-D homogeneous coordinate extension to the CORE by <PLOT79>. Since 2-D applications will probably be more common, the convention is adopted for input of sequences of numbers, including those representing a point coordinate, that any omitted values default to zero, unless the command has provided other defaults for those numbers. For 4-D homogeneous coordinates, however, the fourth coordinate is assumed to be one unless explicitly specified. Thus, the commands "MOVE", "MOVE 0", "MOVE 0 0", "MOVE 0 0 0", and "MOVE 0 0 0 1" are all equivalent. Similarly, "LINE 2 1", "LINE 2 1 0", and "LINE 2 1 0 1" have the same effect.