Here each non-zero O-D entry occupies a single line or record giving some (possibly all) of the following:
(i) sequential row and column numbers;
(ii) low and column zone names;
(iii) the matrix level (in the case of a stacked matrix);
(iv) the block (if stacked by blocks);
(v) the cell value.
Of these either i) and ii) (or both) are mandatory, iii) and iv) are generally not used and v) is mandatory. Choices for the contents are defined interactively by the user prior to input.
The records may either be read “formatted” (i.e. in pre-defined fixed columns) or “free format/CSV” (i.e. with each record separated from its neighbours by one or more spaces and/or commas). Note that fixed column data may also be read as though it were free format (provided that there is always at least one space between adjacent entries) but the converse is not true. It is strongly recommended that the free format input option is selected. (With 10.6 it is now the default.)
Note that the form and contents of the input data must be fully and correctly specified by the user interactively prior to reading in the data, otherwise input errors will almost certainly result.
For the moment header records, etc. cannot be explicitly included with single records although, if they do appear, they will cause non-fatal read errors which do not affect the final output matrix.