The Data Packet is a location in application storage where the physical mouse device driver returns to the caller a 1-WORD current mouse Event Mask. The format of the Data Packet is as follows:
┌──────────────────────────────────────┐ │Field Length C Datatype │ ├──────────────────────────────────────┤ │Event Mask WORD USHORT │ └──────────────────────────────────────┘