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.
This makes no comment on how long something takes to run or how much memory it uses, but how its increase depends on the size of the input.
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.
This creates a so-called protocol overhead as the additional data does not contribute to the intrinsic meaning of the message.
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.