simplest form of the INPUT statement uses list input. List input is
used to read data values that are separated by a delimiter character
(by default, a blank space). With list input, SAS reads a data value
until it encounters a blank space. SAS assumes that the value has
ended and assigns the data to the appropriate variable in the program
data vector. SAS continues to scan the record until it reaches a non-blank
character again. SAS reads a data value until it encounters a blank
space or the end of the input record.