Overhead (engineering)

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In engineering, some methods or components make special demands on the system. The extra design features necessary to accommodate these demands are called overhead. For instance, in electrical engineering, a particular integrated circuit might draw large current, requiring a robust power delivery circuit and a heat-dissipation mechanism.

Example[edit]

An example from software engineering is the encoding of information and data. The date and time "2011-07-12 07:18:47" can be expressed as Unix time with the 32-bit signed integer 1310447927, consuming only 4 bytes. 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. As XML this date can be written as follows with an overhead of 218 characters, while adding the semantic context that it is a CHANGEDATE with index 1.

<?xml version="1.0" encoding="UTF-8"?>
<DATETIME qualifier="CHANGEDATE" index="1">
    <YEAR>2011</YEAR>
    <MONTH>07</MONTH>
    <DAY>12</DAY>
    <HOUR>07</HOUR>
    <MINUTE>18</MINUTE>
    <SECOND>47</SECOND>
</DATETIME>

The 349 bytes resulting from the UTF-8 encoded XML correspond to a size overhead of 8625% over the original integer representation.

See also[edit]