A Small piece of data inSerted in order to achieve a deSired memory alignment or other addreSSing property. For example, the PDP-11Unixlinker, in Split I&D (inStructionS and data) mode, inSertS a two-byteShim at location 0 in data Space So that no data object will have an addreSS of 0 (and be confuSed with the C null pointer). See alSo looSe byteS. [Jargon File] (1994-12-21)