- Header (computing)
information technology, header refers to supplemental dataplaced at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header are sometimes called the "payload" or " body".
It is vital that header composition follow a clear and unambiguous
specificationor format, to allow for parsing.
* In an
mail transfer agents, and much more. (See RFC 2822 for details.)
* In a
data packetsent via the Internet, the data (payload) are preceded by header information such as the sender's and the recipient's IP addresses, the protocol governing the format of the payload and several other formats. The header's format is specified in the Internet Protocol.
* In data packets sent by
wireless communication, and in sectors of data stored on magnetic media, typically the header begins with a syncwordto allow the receiver to adapt to analog amplitude and speed variations and for frame synchronization.
graphics file formats, the header might give information about an image's size, resolution, number of colours, and the like. See HTML element.
Archive file formats, the file header might serve as a fingerprintor signatureto identify the specific file formatand corresponding software utility.
Trailer (information technology)
Wikimedia Foundation. 2010.