Arguments specifying options are usually of type CHARACTER*1. The meaning of each valid value is given, as in this example:
The corresponding lower-case characters may be supplied (with the same meaning), but any other value is illegal (see subsection 5.1.9).
A longer character string can be passed as the actual argument, making the calling program more readable, but only the first character is significant; this is a standard feature of Fortran 77. For example:
CALL SPOTRS('upper', . . . )