A refinement in calipers is the replacement of the analog dial with an electronic digital display on which the reading is displayed. Some digital calipers can be switched between metric and inch units. All provide for zeroing the display at any point along the slide, allowing the same sort of differential measurements as with the dial caliper but without the need to read numbers that may be upside down. Digital calipers may contain some sort of "reading hold" feature, allowing the reading of dimensions even in awkward locations where the display cannot be seen. Even with all of these benefits, digital calipers have by no means replaced the dial caliper. Digital calipers typically do not have the beam structure of a dial or vernier caliper and therefore do not have the repeatability or accuracy to an amateur user. Digital calipers offer a serial data output. Measurements can be taken and instantly stored in a spreadsheet or similar piece of software, significantly decreasing the time taken to take and record a series of measurements. Like dial calipers, the slide of a digital caliper can usually be locked using a lever or thumb-screw. Both dial and digital calipers can be used with accessories that extend their usefulness.