The data read from an input .dat file may be based on either sequential or numerical zone names (10.2.2) or indeed both as is the case with the standard SATURN - formatted data files (10.5.1). With other formats (e.g. spread-sheet, 10.5.5) there is no explicit mention of either row or column numbers but they are implied by the position of the entry within the data file.
Note that in certain cases it may be possible to “pre-define” the numerical zone numbers before reading in the .dat file. Thus if the .dat file updates an existing input .ufm matrix the zone names will already have been obtained from the .ufm file. Alternatively the names may be obtained from a corresponding network .ufs file (10.3.3). If the names are pre-defined this allows the input .dat file to use those names instead of sequential numbers which may be more convenient for the users.
Within 3) and 5) above it is possible to establish the zone names by carrying out a preliminary “pre-pass” through the .dat file.