ta is distinguished from other contrasting forms of information on which computers operate, such as text, graphics, speech, and image. The distinguishing characteristic is that it is organized in a structured, repetitive, and often compressed way. Typically the structure takes the form of sets of fields, where the field names are omitted (this omission being a main means of achieving compression). The “meaning” of such data is not apparent to anyone who does not know what each field signifies (for example, 