The plot request plots the values of High on the vertical axis and the values of Year on the horizontal axis. It also specifies an asterisk as the plotting symbol. HAXIS= specifies that the horizontal axis will show the values 1950 to 1995 in five-year increments. VREF= draws a reference line that extends from the value 3000 on the vertical axis.
proc plot data=djia;
   plot high*year='*' / haxis=1950 to 1995 by 5 vref=3000;
   title 'High Values of Dow Jones Industrial Average';
   title2 'from 1954 to 1994';