Prefix 2C used before the instructions X~Mxx, Minxx, MRxx, M-xx, M+xx causes them to access memory locations from 20 to 39.
Prefix 2D selects memory locations from 40 to 59.
Prefix 2E selects memory locations from 60 to 79.
Also, the instruction codes RND0..RND9 preceded by the prefix 2C form instructions FIX0..FIX9.
The code table kindly contributed by Mahmoud Yassine.