A unit for expressing the capacity of
memory equal to 2**10 = 1024
characters. If the characters are
binary, one K equals 1024
bits. But if there are N kinds of characters, (e.g., 10 numerals of the decimal system, and/or 2 x 26 upper case and lower case letters of standard English) K = 1024 log_2 N
bits of storable
information . Because N is variable, K is a meaningful quantity only in the
context of the knowledge of the number of characters involved. E.g., in English word processing systems, N is determined by the keyboard of the
input device. (
Krippendorff )