A NID is a Node ID. It is useful to use NIDs in programs that access MDSplus nodes. In general, use GETNCI to get a list of NIDs that satisfy some criteria, then use these NIDs in subsequent calls to GETNCI. For example, this code fragment gets the NIDs, full path names, and min path names of all the signal nodes in the tree subtree. ;; Get NIDs, FULLPATH, and MINPATH of signal nodes. nids = mdsvalue('GETNCI("\\'+tree+'::TOP***","NID_NUMBER","SIGNAL")') full_paths = mdsvalue('GETNCI($,"FULLPATH")',nids) min_paths = mdsvalue('GETNCI($,"MINPATH")',nids) The first call to GETNCI returns the NIDs, which are then used in the subsequent GETNCI calls.