flat
1. Lacking any complex internal structure. "That {bitty box}
has only a flat file system, not a hierarchical one." The verb
form is {flatten}. Usually used pejoratively (at least with
respect to file systems).
2. Said of a memory architecture like that of the {VAX} or
{Motorola} {680x0} that is one big linear address space
(typically with each possible value of a processor register
corresponding to a unique address). This is a {Good Thing}.
The opposite is a "{segmented}" architecture like that of the
{Intel 80x86} in which addresses are composed from a
base-register/offset pair. Segmented designs are generally
considered cretinous.
3. A flat {domain} is one where all elements except {bottom}
are incomparable (equally well defined). E.g. the integers.
[{Jargon File}]