HBOOK files are in fact ZEBRA RZ files [10].
Input/output error return codes are available
vin the ZEBRA communication vector IQUEST,
and the user should consult the RZ manual for their meaning.
Both disk and memory resident files are supported, the latter being
particularly useful in online applications,
where histogram data have to be shared between different processes.
HBOOK files are written in Zebra exchange format and thus
need not be converted when transferred between different computer
systems using binary ftp (see section 
),
or accessed over the network using
a distributed file system such as AFS or NFS.