Overhead in computer systems consists of shared functions that benefit all users or processes but are not directly attributable to any specific task.
Overhead can be a deciding factor in software design, with regard to structure, error correction, and feature inclusion.
In software engineering, overhead can influence the decision whether or not to include features in new products, or indeed whether to fix bugs.
Overhead is deliberately not part of this calculation, since it varies from one machine to another, whereas the fundamental running time of an algorithm does not.
This should be contrasted with algorithmic efficiency, which takes into account all kinds of resources – a combination (though not a trivial one) of complexity and overhead.
Represented as ISO 8601 formatted UTF-8 encoded string 2011-07-12 07:18:47 the date would consume 19 bytes, a size overhead of 375% over the binary integer representation.