A blockchain[1][2][3]—originally, block chain[4][5]—is a distributed database that maintains a continuously-growing list of data records secured from tampering and revision. It consists of data structure blocks—which hold exclusively data in initial blockchain implementations[6][not in citation given] and both data and programs in some more recent implementations—with each block holding batches of individual transactions and the results of any blockchain executables.[7][better source needed] Each block contains a timestamp and a link to a previous block