Stack Files using SAS

Test file is a file that increase yearly. I am trying to stack the file using a loop. The loop successfully read in the yearly file. But cannot do the stacking.
Please help !

%let yyyy = 2010; /*Keep increasing*/
%macro test(stop=&yyyy);
%DO i=2000 %to &stop;

FILENAME A_O "C:\test_&i..dat";
data iterate1;
INFILE A_O LRECL=2 truncover END=EOF;
INPUT
@1 A $CHAR1.
@10 B $CHAR1.
;
run;

/*How to do the stacking here?*/
DATA STACK;
SET iterate1;
RUN;

%END;
%mend;
%test;