h saveold
saveold saves the dataset currently in memory on disk under the name
filename in Stata 9/Stata 10 format. Stata 11 has the same dataset format
as Stata 10, but Stata 11 is smart enough to read Stata 12 datasets.
If you are using Stata 12 and want to save a file so that it may be read
by someone using Stata 9 or Stata 10, simply use the saveold command.