open

(1) To engage a disk or tape file for reading and writing. The open procedure "locks on" to an existing file. Contrast with close.

(2) With regard to a switch, open is "off."

(3) Made to operate with other products. See open architecture, open system and open source.

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1.		open - To prepare to read or write a file. This usually involves checking whether the file already exists and that the user has the necessary authorisation to read or write it. The result of a successful open is usually some kind of capability (e.g. a Unix file descriptor) - a token that the user passes back to the system in order to access the file without further checks and finally to close the file.
2.		open - Abbreviation for "open (or left) parenthesis" - used when necessary to eliminate oral ambiguity. To read aloud the LISP form (DEFUN FOO (X) (PLUS X 1)) one might say: "Open defun foo, open eks close, open, plus eks one, close close."
3.		open - Non-proprietary. An open standard is one which can be used without payment.