This diagram from the New Zealand Resuscitation Council shows the DRS ABC.
D is to Check for Danger
R is to Check for Responsiveness
S is to Shout for help – ask a bystander to dial 111 and ask for an ambulance
A is to Open airway
B is to Check for Breathing – if not breathing, start CPR. Otherwise, if alone, leave the victim and dial 111
C is for CPR 30:2 – thirty chest compressions, followed by opening the airway and giving two breaths.