All information used in computer systems is transformed in a series of bits 0 and 1, represented by an electromagnetic state, and stored in a digital media. A series of bit, called byte, is the smallest addressable element for a given computer architecture and can represent anything we want to, be it alphanumeric characters or a pixel in a bitmap image etc (Butterworth, R. & Dykes, J).
Collections of digital information referred as files contain series of bytes, and computers interpret them according to rules known as file formats. The operating system is aware of the files physical locations on the disk enabling users to access them via an interface. Additional data, called metadata exist within the files providing information about the contents. Search engines categorise the web pages using metadata information stored in HTML meta elements. (Butterworth, R. & Dykes, J).
But information is not just text, could also be presented in the form of a graphics. Different technologies provide mechanisms to enable graphical information presented in electronic documents. Embedding, or file-centred view, facilitates the document distribution in different environments and has all graphics and external data included in the binary file. Linking, or document-centred view used in a local environment and has any external data linked, with changes to the linked data reflected on the container document.(Butterworth, R. & Dykes, J).
On the Internet, the usual approach is document-centred; the web pages contain links to the server's filesystem and the browser then http-request the image from there. Other options use a file-centred view via data urls : instead of linking to an image stored locally on the server, the image is provided within the URL itself as a base64-encoded string. A drawback to this method is that the browser is not caching the image and downloads it every time is used, but this can be minimized with the use of CSS(http://www.sveinbjorn.org/dataurls_css).
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