Header
In computing, the term "header" can refer to a number of different things. Some of the most common uses include 1) a document header, 2) a webpage header, and 3) a file header.
1. Document Header
Many word processing programs allow you to add a header and/or footer to each page. The header is a small area at the top of the document, while the footer is located at the bottom. Document headers are often used to display the document title or company name at the top of each page. By default, the header content is the same on all pages, so when you edit the header on one page, it will update on all the other pages as well. If you break a document up into sections, you can specify different headers for each section.
Word processors provide different ways of adding and editing header content. Several programs allow you to select to display the header and footer content. Once visible, you can type new content inside each section. Most version of Microsoft Word allow you to simply double-click in the header area to activate the header and add or edit text. If you want to change the height of the header, you can open the Document Formatting window and modify the margins.
2. Webpage Header
The header of a webpage typically includes the company or organization's logo, as well as the main navigation bar. This section, which resides at the top of each webpage, is often part of a template and therefore is the same across all pages within a website or section of a website. HTML 5 even includes a <header> tag that developers can use to specify the header section of each webpage.
NOTE: A webpage header should not be confused with the <head> section in the HTML, which includes the page title, meta tags, and links to referenced files.
3. File Header
A file header is a small amount of data at the beginning of a file. File headers vary between file formats, but they generally define the content of the file and list specific file attributes. For example, the file header of a JPEG image file may include the image format, color profile, and application that created the file. An MP3 audio file may include the song name, tagging format, and compression information. You can view a file's header by dragging the file icon to a text editor and reading the first few lines. While binary files may contain a lot of garbled characters, the header information is often still readable.
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