SAS uses a number that you provide, called a seed, to start its random number generation for
the first random number you ask to be generated. The first random number then becomes the
seed for the second; the second, for the third, etc. If you use the seed number 0, then SAS
will begin its random number generation based on the time of day, according to the computer,
at which you issued the command. You can also use positive integers as seed values.