Information must be distinguished from any medium capable of carrying it. A physical medium (such as a magnetic disk) may carry a logical medium (data, such as binary or text symbols). The information content of any physical objects, or logical data, cann

Information must be distinguished from any medium capable of carrying it. A physical medium (such as a magnetic disk) may carry a logical medium (data, such as binary or text symbols). The information content of any physical objects, or logical data, cannot be measured or discussed until it is known what range of possibilities existed before and after they were received. The information lies in the reduction in uncertainty resulting from the receipt of the objects or the data, and not in the size of complexity of the objects or data themselves. Questions of the form, function, and semantic import of data are only relevant to information inasmuch as they contribute to the reduction of uncertainty. If an identical memorandum is received twice, it does not convey twice the information that its first occurrence conveyed: the second occurrence conveys no information at all, unless, by prior agreement, the number of occurrences is itself to be regarded as significant.