human: What are the IPC editions/versions?
assistant: The IPC is periodically revised for improving the system and for reflecting technical developments in its contents. Between 1968 and 2006, the IPC was revised roughly every five years and, after each revision, a new edition was published. The eighth edition of the IPC entered into force on January 1, 2006. Since 2006, the IPC has been revised more frequently and each edition, called also version, is indicated by the year and month of its entry into force. Since 2010, the IPC is revised once a year and each new version enters into force on January 1. Six months in advance, the new scheme, compilation and revision concordance files are available for download or consultation. The version indicator gives the edition/version where the corresponding entry was introduced in the IPC as a new entry or where its "file scope" was modified, for example [4] or [2008.01]. New entries are progressively introduced in new IPC versions because there are new emerging technologies for which the coverage was not sufficient in the previous versions. In addition, existing classification places can be modified because their original design does not fit the needs of the patent classification. Often, they can be transferred to newly created places where a new, more appropriate classification tree, can be elaborated. With the reformed IPC, generally, there should be no need to use previous IPC versions for search because a major part of patent files was supposed to be reclassified according to the revision changes. However, in some areas, the reclassification works are delayed, thus it is highly recommended to consider version indicators for IPC-based search and to use the Revision Concordance List to identify relevant IPC symbols for previous IPC versions. Please note the IPC Warnings warning assigned to such places where reclassification has not yet been completed. (See also paragraphs 8 to 10bis and 42 of the “ Guide to the IPC ” for more information.)