Today the term data is associated in many peoples’ minds mainly with computers. However, data (as in “given facts” or measurements) has been used as a term by scientists and scholars for centuries. Just as with a counting bead, a notch in a stick, or a handwritten tally, data as stored in a com-puter (or on digital media) is a representation of facts about the world. These facts might be temperature readings, cus-tomer addresses, dots in an image, the characteristics of a sound at a given instant, or any number of other things. But because computer data is not a fact but a representation of facts, its accuracy and usefulness depends not only on the accuracy of the original data, but on its context in the computer.
At bottom, computer data consists of binary states (rep-resented numerically as ones or zeroes) stored using some physical characteristic such as an electrical or magnetic charge or a spot capable of absorbing or reflecting light. A string of ones and zeroes in a computer has no inherent meaning. Is the bit pattern 01000001 a number equivalent to 65 in the decimal system? Yes. Is it the capital letter “A”? It may be, if interpreted as an ASCII character code. Is it part of some larger number? Again, it may be, if the mem-ory location containing this pattern is interpreted as part of a set of two, four, or more memory locations.
In order to be interpreted, data must be assigned a cat-egory such as integer, floating point (decimal), or character (see data types). The programming language compiler uses the data type to determine how many memory locations make up that data item, and which bits in memory corre-spond to which bits in the actual number. Data items can be treated as a batch (see array) for convenience, or different kinds of data such as names, addresses, and Social Security numbers can be grouped together into records or structures that correspond to an entity of interest (such as a customer). In creating a structure within the program to represent the data, the programmer must be cognizant of its purpose and intended use.
The programming language and code statements define the context of data within the rules of the language. How-ever, the meaning of data must ultimately be constructed by the human beings who use it. For example, whether a test score is good, bad, or indifferent is not a characteris-tic of the data itself, but is determined by the purposes of the test designer. This is why a distinction is often made between data, as raw numbers or characters, and informa-tion as data that has been placed in a meaningful context so that it can be useful and perhaps even enlightening to the user.
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