A ROOT file is mostly a suite of consecutive data records with the following format <Name>
;<Cycle>
uniquely identifies the record in a directory
----------TKey-(never compressed)-------------- byte 0->3 Nbytes = Number of bytes in compressed record (Tkey+data) TKey::fNbytes 4->5 Version = TKey class version identifier TKey::fVersion 6->9 ObjLen = Number of bytes of uncompressed data TKey::fObjLen 10->13 Datime = Date and time when record was written to file TKey::fDatime | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second 14->15 KeyLen = Number of bytes in key structure (TKey) TKey::fKeyLen 16->17 Cycle = Cycle of key (e.g. 1) TKey::fCycle 18->21 SeekKey = Byte offset of record itself (consistency check) TKey::fSeekKey 22->25 SeekPdir = Byte offset of parent directory record TKey::fSeekPdir 26->26 lname = Number of bytes in the class name TKey::fClassName 27->.. ClassName = Object Class Name TKey::fClassName 0->0 lname = Number of bytes in the object name TNamed::fName 1->.. Name = lName bytes with the name of the object TNamed::fName 0->0 lTitle = Number of bytes in the object title TNamed::fTitle 1->.. Title = lTitle bytes with the title of the object TNamed::fTitle ----------DATA---(may be compressed)----------- 0->.. The data object itself. For an example, see Format of a class object in DATA