[From the Preface to the 3rd Edition:]

From the outset it was obvious to me that a standard work on English usage needed to be based on satisfactory modern evidence and that a great deal of this evidence could be obtained and classified by electronic means. In September 1986, after the completion of the Supplement to the OED and the New Zealand Pocket Oxford Dictionary, and coinciding with other work, including the editing of a volume of essays called Studies in Lexicography, I obtained a personal computer and began to establish a database consisting of ten independent fields corresponding to obvious categories of grammar and usage. The ten fields were adjectives, adverbs, concord, gerunds, infinitives, nouns and articles, ordinaries (a convenient term for points of disputed usage), passives, pronouns, and subjunctives. The fields that I created enabled me to assign specific numbers to the various types of gerunds, passives, subjunctives, etc., and these types soon began to multiply as my reading of sources continued. The numbering system enabled me to retrieve and print out all examples of a specified type, e.g. gerunds 3 = possessive with gerund: I was proud of his being accepted at such a good school—New Yorker, 1986; and gerunds 4 = possessive not used with gerund: how could she think of the baby being born in the house—A. S. Byatt, 1985- In the end my gerunds field contained examples of more than 100 types of gerundial constructions, and, like all my fields, it is infinitely extendible. Some of the fields, and especially the one containing examples of constructions in which infinitives occur, are much larger. The ordinaries field contains, for example, a formidable array of controversial uses of due to, like used as a conjunction, of used by children and poorly educated people to mean 'have', unattached participles, irregular or unstable past tenses of verbs, e.g. hove/heaved, sneaked/snuck, spelled/spelt, and numerous other type including try and (used beside try to) followed by an infinitive.

The database was programmed in such a way that I could retrieve from it all examples of specified words that randomly occurred in the sentences keyed in for other purposes—words such as about, better, if, more, though, too and also specified parts of words, e.g. all words in the database that happened to end in -eddy (allegedly, markedly, etc.). This database is small by the standards of the great university- and business-based corpora. But its value lies in the fact that it contains material from sources that I have selected myself, and examples that I have chosen and keyed in myself—in computer terminology, it contains no garbage. It is a private, personalized database of English uses and constructions of the 1980s and 1990s. By 1990 the time consuming process of collecting and classifying evidence needed to be modified, as the writing of articles for the book, which I had begun in August 1987, had only reached the end of the letter C by October 1990. From then onward I continued to build up my paper-slipfiles,but began to rely much more than hitherto on the evidence available in the OED Department's electronic and paper-slip files (see the Acknowledgements on p. xiii).