data coding;
set sample;

x1_h = ( x1 in ('GGG','TTT'));
X2_H = ( X2 > 2200);
RUN;

X1_h is the dummy variable when x1 has character values.  X2_h is the dummy variable when x2 has numerical values. The max and min values of x1_h/x2_h is 1 and 0. You can create dummy variables like these based on the values of x variables.

You can consider using glmmod procedure to code the dummy automatically like SAS GLM procedure does.

Here is an example to illustrate this concept.

proc print data=sashelp.class;
run;

data class;
  set sashelp.class;
  id=_N_;
  run;

proc glmmod data=class outdesign=out  noprint;
class age ;
model id=age ;
run;

proc print data=out label;
run;