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The process of obtaining statistical data from documents not primarily designed for this purpose is called extraction^{1}. Data may be extracted from documents mechanically^{2} by using tabulating machinery^{3} or punched card machines^{3}.
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To extract information mechanically it is first necessary to code^{1} the information on the basic document^{2}. This process consists of the translation of the information into numerical form by means of code numbers^{3}. The key by which this information is translated is known as a coding scheme^{4}. Such a scheme limits possible subdivision of the data, but in the ultimate tabulation or breakdown certain codes may be shown in combination. A combination of individual codes may be called a classification^{5} (cf. 1307*) where the information is shown under certain heads^{6} (cf. 1102) or headings^{6}.
 1. code n. — code v. — coder n'., one who codes.
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There are four fundamental operations in mechanical tabulation. Punching^{1} consists of the transfer of the information to a punched card^{2} sometimes called a punch card^{2}. The information is shown on that card by punching a hole in a given position. Verification^{3} is the process of checking the accuracy of the punching. Sorting^{4} is the arrangement of cards in a certain order, and tabulation^{5} consists of counting the cards or the information on them in certain groups and totalling^{6} them in these groups. The mechanical tabulation of data is in process of very rapid development and new terms and operations are being introduced almost continuously. Thus mark sensing^{7} is a process by which pencil marks on a document are automatically translated into punched holes on the same document. This operation has the effect of mechanizing the two manual processes of punching and verification.
 3. verification n. — verify v. 5. tabulation n. — tabulate v.
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The machines used in these operations are the punch^{1}, verifier^{2}, sorter^{3} and tabulator^{4}. Other machines used in mechanical tabulation are the reproducer^{5}, which copies information from one punched card to another, the interpreter^{6}, which converts the information contained on the cards as punched holes into print on the card, and the collator^{7}, which is used for the comparison or merging of different packs of cards. The summary punch^{8} is used for preparing cards, sometimes called summary cards^{9}, containing intermediate totals, which can then be used in later tabulations.
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Adding machines^{1} are used for the processes of addition and subtraction, the term calculating machine^{2} being in general reserved for machines capable of performing also multiplication and division. Small calculating machines and adding machines are often referred to as desk machines^{3}, The multiplier^{4} is a punched card machine, which performs certain calculations and punches the results on the cards containing the original data. Electronic computing^{5} makes it possible to perform a large number of calculations within a very short space of time. The machines that do this are electronic computers^{6}.
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Sliderules^{1} are used as an aid to calculations. Nomographic methods of computation^{2} may also be used. A nomogram^{3} is a figure (1552) whereby calculations can often be made at sight.
 3. nomography n., the part of mathematics dealing with the construction and use of nomograms.
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