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3.  ^F\\ILES AND ^DEVICES.
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^^VERSION: ASDDJK781030\\
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^THE DEVICES ON A COMPUTER SYSTEM ARE USED TO INPUT, STORE,
AND OUTPUT DATA.
^THE DATA ARE ORGANIZED INTO UNITS, CALLED RECORDS, WHICH
ARE HANDLED INDIVIDUALLY BY THE COMPUTER SYSTEM.
^ONE CHARACTERISTIC OF A RECORD IS THAT ITS TRANSFER
IS ACCOMPLISHED WITH A SINGLE OPERATION, SO THAT
A RECORD IS THE SMALLEST UNIT OF DATA FOR ^^I/O\\
PURPOSES.
^EXAMPLES OF RECORDS ARE: A LINE OF TEXT TYPED AT A TERMINAL,
A STRING OF COORDINATES FROM A DIGITIZER, AND A
SEQUENCE OF NUMBERS ON MAGNETIC TAPE.
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^MOST DEVICES ARE ABLE TO TRANSFER RECORDS SEQUENTIALLY ONLY, AND THEREFORE
ONLY CAN BE USED BY ONE TASK AT A TIME.
^TO PROVIDE MANY SIMULTANEOUS USERS WITH DATA HANDLING FACILITIES 
WOULD REQUIRE MANY SUCH DEVICES.
^A SOLUTION TO THIS PROBLEM IS A FILE SYSTEM, WHEREBY MANY AREAS ON A
RANDOM-ACCESS DEVICE (USUALLY A DISK) CAN BE ACCESSIBLE
SIMULTANEOUSLY, AND A SYSTEM PROGRAM ENSURES THAT
EACH TRANSFER IS DIRECTED TO THE PROPER AREA.
^THUS A FILE SYSTEM PROVIDES THE APPEARANCE OF MANY INDIVIDUAL SEQUENTIAL 
DEVICES.
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^A FILE IS A USER-NAMED AREA ON A MASS STORAGE DEVICE (DISK OR MAGNETIC
TAPE), CONSISTING OF A COLLECTION OF RECORDS.
^FILES ARE IDENTIFIED BY A FILE SPECIFIER IN THE FOLLOWING FORMAT:
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DEV:[G,M]FILENAME.TYP;VER
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###########E.G.  ^^DM1:[231,11]PROGRAM1.FTN;32\\
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WHERE:
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DEV:	IS THE  PHYSICAL DEVICE ON  WHICH  THE  	##^^DM1:\\
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VOLUME CONTAINING THE
DESIRED FILE IS MOUNTED.
^THE DEVICE NAME CONSISTS OF TWO CHARACTERS FOLLOWED BY A ONE OR TWO 
DIGIT (OCTAL) UNIT NUMBER AND A COLON.
^NOTE THAT THE COLON IS PART OF THE DEVICE NAME.
^SEE ^APPENDIX ^D FOR A LIST OF DEVICES ON THIS SYSTEM.
^IF NO DEVICE IS SPECIFIED,#^^SY0:\\ IS ASSUMED.
^IF NO UNIT NUMBER IS SPECIFIED, "0" IS ASSUMED.
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[G,M]	IS THE USER IDENTIFICATION CODE (^^UIC\\),	[231,11]
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WHICH IDENTIFIES THE DIRECTORY CONTAINING THE FILE.
G AND M ARE OCTAL NUMBERS IN THE RANGE 1 TO 377,
IDENTIFYING THE GROUP AND THE MEMBER OF THE
GROUP, RESPECTIVELY.
^NOTE THAT THE SQUARE BRACKETS ARE PART OF THE ^^UIC\\.
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FILENAME	IS THE NAME OF THE FILE,  WHICH MAY BE 	^^PROGRAM1\\
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UP TO NINE ALPHANUMERIC CHARACTERS IN LENGTH;#MORE
THAN NINE ARE IGNORED.
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^FILENAME AND FILE TYPE ARE ALWAYS SEP- 	###.
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ARATED BY A PERIOD, WHICH IS NOT A PART OF
EITHER THE FILENAME OR THE FILE TYPE.
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TYP	IS THE FILE TYPE, AND IS USED TO INDI-	##^^FTN\\
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CATE THE FORM OF THE FILE.
^FILE TYPE MAY BE UP TO THREE ALPHANUMERIC CHARACTERS, AND
WHILE THERE ARE NO RESTRICTIONS ON THE FILE TYPES A USER
MAY USE, THERE ARE CERTAIN RECOMMENDED SYSTEM DEFAULTS, FOR
EXAMPLE:
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^^FTN - FORTRAN\\ SOURCE CODE.
^^OBJ\\ - OBJECT CODE.
^^TSK\\ - TASK IMAGE.
^^DAT\\ - DATA RECORDS.
^^CMD\\ - COMMANDS.
^^TMP\\ - TEMPORARY FILE.
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^A COMPLETE LIST OF PREFERRED SYSTEM FILE TYPES IS INCLUDED IN THE
^^PIP\\ DOCUMENTATION.#(^APPENDIX ^B.)
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^FILE TYPE AND VERSION NUMBER ARE SEP- 	###;
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ARATED BY A SEMICOLON, WHICH IS NOT A PART OF
EITHER THE FILE TYPE OR THE VERSION NUMBER.
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VER	IS AN OCTAL NUMBER USED TO DIFFERENTI-	##32
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ATE AMONG VERSIONS
OF A FILE.
^FOR EXAMPLE, A FILE CREATED BY THE EDITOR WOULD HAVE A VERSION 
NUMBER OF 1.
^IF THE FILE IS EDITED AGAIN, THE ORIGINAL FILE WILL
BE KEPT FOR BACKUP, AND THE NEW FILE WILL HAVE THE SAME FILENAME
AND FILE TYPE, BUT A VERSION NUMBER OF 2.