A lathe is usually set for diameter programing, IOW if you program a diameter in the X the distance moved by the axis is a radius value. As an actual distance moved in the X results in 2x this removed from the diameter.
Also the canned programs are usually tailored to lathe functions such as complex thread cycles etc.
Another feature a lathe often has is CSF Constant Surface Feed, which will proportionally increase the spindle rpm as the X axis value approaches axis centre, this feature maintains the surface feed under the tool which would normally reduce as the cut diameter decreases.
Al.