DATA Q; INPUT Trt $ @@; DO Replication = 1 TO 4; INPUT Y @; OUTPUT; END; CARDS; Trt1 23 27 19 21 Trt2 18 17 20 15 Trt3 29 31 32 34

proc print; RUN;

If I run this in SAS, I obtain the following output:

Obs	Trt	Replication	Y
1	Trt1	1	23
2	Trt1	2	27
3	Trt1	3	19
4	Trt1	4	21
5	Trt2	1	18
6	Trt2	2	17
7	Trt2	3	20
8	Trt2	4	15
9	Trt3	1	29
10	Trt3	2	31
11	Trt3	3	32
12	Trt3	4	34

Could you give me a break down of how this result is obtained?