sir pls tell me how to find the ZERO ERROR and LEAST COUNT along with two or three solved questions relating to zero error and least count

Zero Error

It is a defect in a measuring device (Vernier Callipers & Screw Gauge).   When jaws of a Vernier Callipers or Screw Gauge are closed, zero of main scale must coincides with the   zero of vernier scale or circular scale in case of screw gauge.   If they do not coincide then it is said that a zero error is present in the instrument.   Least Count     Minimum measurement that can be made by a measuring device is known as " LEAST COUNT'.   Least count (vernier callipers) = minimum measurement on main scale / total number of divisions on                                                                                                              vernier scale .   Least count (screw gauge) = minimum measurement on main scale / total number of divisions on                                                                                                    circular scale