Certain fields on a data record may be left blank. The program will supply appropriate default values. The is the basic default mechanism for the Aqwa suite (but see Default Values below). The fields which may be left blank are indicated in the appropriate places in the text (The Preliminary Data (Data Category 0)).

Note that, due to a peculiarity of the Fortran language, the program cannot distinguish between a blank field and one in which a zero value has been entered. Therefore, if zero is entered in a field which the manual indicates can take default values, the default value (which may be non-zero) will be invoked.