JEITA CP-3451 - 4 - 4    Exif Image File Specification 4.1    Outline of the Exif Image File Specification This chapter gives details of the image file specification, covering the following items: ·  Format version definition, ·  Specifications relating to image data, ·  Basic structure of image data, ·  Tags, ·  JPEG marker segments, ·  Specifications on data recording. 4.2    Format Version The version of the format specified here is recorded as 4 bytes (see section 4.6.5). The address bytes are recorded as A1, A2, B1, and B2, starting with the lowest number. A1 and A2 store the upper part of the standard version, with  the  lower  part  stored  in  B1  and  B2.  When  changes  are  made  to  the  version  number  of  this  standard,  the following rules apply. ·  When  the changes  are such  that  data readers can properly recognize  conventional  information  and skip  the data that was recorded using newly added functions, the lower part of the version (B1, B2) is changed. ·  When there is a possibility that a data reader implementing the old standard may operate incorrectly due to the new specifications, the upper part of the version (A1, A2) is changed.   Players should be able to play back files of versions earlier than the supported standard. 4.3    Definition of Glossary Terms and notation are used as follows in this standard: ·  "Tag" is used as a synonym of "field", ·  ".H" appended to a numerical value means it is hexadecimal notation, ·  Unless otherwise indicated, other numerical values are given in decimal notation, ·  The initial IFD in a file is the "0th IFD," with the next IFD being called the 1st IFD,