Before matrix cells can be input it is necessary to know in advance the number of rows and columns (generally the same) in the matrix so that the values can be stored in their correct cell positions as they are read in. A similar problem is to establish the zonal names in advance – see below.
With SATURN formats (1 above) this information is contained in the initial Namelist records (see 10.5.1). With other formats this information must be supplied interactively by the user (in some cases a “pre-read” of the data file establishes the “names”; see below).