Used to synchronize access to the file control block 用于同步對文件控制塊的訪問。
File control block fc 檔案控制區(qū)塊
百科解釋
A File Control Block (FCB) is a file system structure in which the state of an open file is maintained. An FCB is managed by the operating sytem, but it resides in the memory of the program that uses the file, not in operating system memory.