When one only needs taking a character out of a string, the char function is more efficient than substr by 25%.

885  data _null_ ;
886     length x $1;
887     s = '123456789ABCDEF' ;
888     do j = 1 to 1e7 ;
889        x=substr(s,10);
890     end ;
891     put x=;
892  run ;

x=A
NOTE: DATA statement used (Total process time):
      real time           0.22 seconds
      cpu time            0.21 seconds


893
894  data _null_ ;
895     length x $1;
896     s = '123456789ABCDEF' ;
897     do j = 1 to 1e7 ;
898        x=char(s,10);
899     end ;
900     put x=;
901  run ;

x=A
NOTE: DATA statement used (Total process time):
      real time           0.16 seconds
      cpu time            0.15 seconds