Once opened, named pipes act more like unnamed pipes than files. Data written to the named pipe is read in FIFO order. Once data written to a named pipe is read, it is removed from the named pipe. Also, the operating system regards individual reads and writes as unbreakable (atomic) units and issues them one at a time, unless the amount read or written exceeds the capacity of the named pipe. The capacity of a named pipe is the same as the capacity of an unnamed pipe. (The capacity of an unnamed pipe depends on the implementation; on UNIX environments, however, the amount is always 4,096 bytes or greater).