1. (filtering) A logical operation carried out on a byte, word, or field
of data in order to modify or identify a part of it. A bit pattern - the same
length as the item to be masked - is generated and stored in a register as a
mask. By use of the appropriate operation, e.g. subtract, logical AND, logical
OR, the mask can be used to suppress bits in the data, or set them to zero, etc.
The process is used for purposes such as identifying the presence of
high-priority bits in a status byte or resetting interrupts.
2. The use of a chemical shield, the mask, to determine the
pattern of interconnects in an integrated circuit. Read-only
memories (ROMs) and programmable logic arrays (PLAs) are customized for their particular
applications by the masking process.