Yes they are still, or were until very recently, in use with the military. I learnt morse and various Q & Z codes during my Army signals training. I belive they no longer teach it unless it is required for a specific job.
Essentially the Q and Z codes where 3 letters which correspond to specific sentences or meanings. 3 letters are much easier to send than the full sentence. It therefore goes on that QNH/QFE was used by the RAF when the radio operators used morse and not voice. BT (those in the know will know
)