Overhead

Overhead refers to memory or other incidental yet essential residual resources that sustain a particular program or system--much like overhead in a retail business.

Detail:

Overhead can be applied to information, such as control, routing, and error checking characters, transmitted along with user data. The term is also used when referring to the need to avoid overloading the network with excessive Usenet postings ("reducing network overhead") or to the reduction in modem speed resulting from the use of error control protocols (due to "increased overhead").