Mask (computing)

In computer science, a mask is a sequence of binary numbers associated with a piece of data of equal length used to inform as to what parts of the data should be examined. A mask can be pictured as being overlain upon the piece of data; a 1 in the mask instructs that the binary datum below should be ignored, while 0s in the mask tells that the data below is to be examined. A common type of mask is a subnetwork mask, which is associated with a computer's IP address and used to tell a router as to how much of the address indicates the subdivision of the network the computer is on and how much indicates which computer within the particular subnetwork it is.