Answer:
Model codes are the codes which used to change the location of a machine from one place to other place to perform specific task.g and M are the model codes which used in machines.
Ex:
G0 ,G1 , G2 ,G80 ,G81 ... For motion
G17 ,G18 , G19 For planer selection
Mo ,M1 , M2 ,M30 ,M60 For Stopping
M6 For tool change
M26 ,27 For clamping