Old School RuneScape uses the British convention for floor numbering: Ground floor, first floor, etc.
The cook is Duke Horacio's personal cook. He usually seems unprepared, but with the player's help, he prepares great food. He is the starting point for the Cook's Assistant and Recipe for Disaster quests. He can be found in the Lumbridge Castle kitchen on the ground floor[U.K. floor].
When the Cook's Assistant quest is completed, the player is granted use of his magical range, which has a lower chance of burning food when compared to other ranges.