# Change index

A change index is a version of a technical drawing, for example . The terms on changes in technical drawings are currently in the standard defined DIN EN ISO 10209 after the DIN 199 was withdrawn -4.

The first version usually has the index 0, with changes this is increased by 1. The current edition therefore has the highest change index. Alternatively, there is the option of displaying the change index in ascending order with letters, ie a, b, c, […], z, aa, ab etc. Usually, capital letters are used for this, whereby the letters "I" and "O" are due to the risk of confusion with "L" and "0" are not allowed. For example, they are omitted when revising from “H” to the following version, so that the next subsequent change is designated as “J”. Use in combination with a maximum of three letters is permitted, ie after “ZZ” there is then “AAA”, then “AAB” etc., until this system is exhausted after a maximum of 13824 ( ) possible combinations. ${\ displaystyle 24 ^ {3}}$

With the help of this information, an easily comprehensible version management is carried out, which also allows older variants to be clearly addressed. In principle, any number of versions can be stored for just one drawing number.