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Trailing-Edge - PDP-10 Archives - decuslib20-03 - decus/20-0098/maggie.doc
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                         MAGGIE.MAC


             PSEUDO RANDOM-ACCESS FOR MAGTAPES





                        JOHN L. MOSS
       FELDBERG COMPUTER CENTER, BRANDEIS UNIVERSITY
                       JANUARY, 1976







                            NOTE

               THIS  DOCUMENTATION  DESCRIBES
               SOFTWARE  AS  OF  V  1A(1)  OF
               MAGGIE AND DOES NOT  REPRESENT
               A  COMMITMENT  FOR  SUPPORT ON
               BEHALF   OF    THE    FELDBERG
               COMPUTER CENTER.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 2
GENERAL PHILOSOPHY


1.0  GENERAL PHILOSOPHY

     MAGGIE IS DESIGNED TO GIVE USERS WITH MEDIUM SIZED DATA
BASE  SYSTEMS THE FLEXIBILITY OF DECTAPES ON A LARGER SCALE.
USERS WHO DO NOT USE PRIVATE FILE STRUCTURES EITHER  BECAUSE
OF  EXCESSIVE COST (CURRENTLY AROUND $350) OR INFREQUENCY OF
USE MAY FIND IT HELPFUL TO  KEEP  FILES  ON  MAGNETIC  TAPE.
MAGGIE  ALLOWS A USER TO REFERENCE FILES BY NAME ON MAGNETIC
TAPE.

     SAFEGUARDS HAVE BEEN IMPLIMENTED  IN  MAGGIE  TO  ALLOW
RECOVERY OF LOST OR MISTAKENLY DELETED FILES.  THE FOLLOWING
SECTIONS DEAL WITH THE COMMANDS FOR MAGGIE AND THE  MODE  OF
STORAGE.




1.1  TAPE STRUCTURE

     A TAPE FORMATTED FOR MAGGIE IS ARRANGED AS FOLLOWS:

        -------------------------
        I                       I
        I  DIRECTORY BLOCK      I
        I                       I
        I.......................I
        I                       I
        I HEADER FILE NUMBER 1  I
        I                       I
        I.......................I
        I ACTUAL FILE NUMBER 1  I
        I                       I
        I.......................I
        I                       I
        I       (ETC)           I
        -------------------------

WHERE THE DIRECTORY FILE IS THE FIRST FILE ON THE TAPE,  AND
EACH  HEADER  FILE CONTAINS THE DIRECTORY ENTRY FOR THE FILE
WHICH FOLLOWS IT.  THE ENTIRE TAPE, INCLUDING  HEADER  FILES
AND DIRECTORY BLOCK, IT RECORDED IN IMAGE BINARY MODE.




1.1.1  STRUCTURE OF DIRECTORY BLOCK - 

     WHENEVER A COMMAND  TO  COPY  TO  TAPE  IS  GIVEN,  THE
FOUR-WORD  LOOKUP  BLOCK  IS SAVED.  AFTER THE FILE HAS BEEN
SUCESSFULLY WRITTEN ONTO TAPE, THE BLOCK IN ITS ENTIRETY  IS
TRANSFERED  TO  THE  DIRECTORY AREA IN CORE AND THUS ENTERED
INTO THE TAPE DIRECTORY.  SINCE  THE  DIRECTORY  IS  WRITTEN
ONTO  THE TAPE ONLY ON COMMAND TO DO SO (/E OR /W COMMANDS),
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 3
GENERAL PHILOSOPHY


THE /S COMMAND HAS BEEN ADDED TO ALLOW THE USER TO DETERMINE
THE  STATUS  OF  HIS  DIRECTORY  IN  CORE.  THE DIRECTORY IS
WRITTEN ONTO THE TAPE ONLY IF IT HAS BEEN  UPDATED  IN  SOME
WAY (COPY TO TAPE, OR DELETE).  THIS ALLOWS THE USER TO HAVE
THE TAPE WRITE-PROTECTED.  THE FOLLOWING IS  AN  OUTLINE  OF
THE FOUR WORD DIRECTORY ENTRY:

        -------------------------
        ISIXBIT/FILENAME/       I
        I.......................I
        ISIXBIT/EXT/,,HD2,DATE 1I
        I.......................I
        IPROT/MODE/TIME/LD2     I
        I.......................I
        ISIZE IN WORDS OR BLKS  I
        -------------------------
        HD2= HIGH CREATION DATE (3 BITS)
        LD2= LOW CREATION DATE (12 BITS)

MAGGIE ADDS A FIFTH WORD TO THIS BLOCK AS SHOWN BELOW.

        -------------------------
        I  (UNUSED),,POSITION   I
        -------------------------

WHERE POSITION IS THE PHYSICAL POSITION ON THE TAPE  OF  THE
HEADER  FILE/FILE  COMBINATION.   THE  DIRECTORY  BLOCK THUS
CONTAINS A SERIES OF FIVE-WORD  ENTRIES  FOR  FILES  ON  THE
TAPE.  A DELETE COMMAND, FOR EXAMPLE, ACTS SIMPLY BY PLACING
A ZERO IN THE FIRST WORD OF THE ENTRY TO BE DELETED.

     IN ADDITION TO THE FILE ENTRIES,  THE  DIRECTORY  BLOCK
CONTAINS  TWO  WORDS OF IDENTIFICATION IN POSITIONS 0 AND 1.
WORD 0 OF THE DIRECTORY BLOCK CONTAINS THE POSITION  OF  THE
LAST  FILE  HEADER/FILE  PAIR,  AND WORD 1 CONTAINS A SIXBIT
TAPE ID.




1.2  FUNCTIONING OF THE COMMANDS

     THE PROGRAM ACTIONS FOR EACH TAPE MANIPULATION  COMMAND
ARE DESCRIBED IN WHAT FOLLOWS.




1.2.1  COPY TO TAPE - 

     THE  PROGRAM  SCANS  THE  USER'S  ENTIRE  UFD  FOR  THE
SPECIFIED  DISK  DEVICE  FOR  EACH  FILESPEC.  IF A MATCH IF
FOUND, THE TAPE IS POSITIONED AT THE END OF  THE  LAST  FILE
AND  THE  NEW HEADER FILE AND FILE ARE WRITTEN.  TAPE IS NOT
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 4
GENERAL PHILOSOPHY


REWOUND.




1.2.2  COPY TO DISK - 

     THE  DIRECTORY  IS  READ  INTO  CORE  (UNLESS  IT   HAS
PREVIOUSLY  BEEN) AND THE CORE DIRECTORY IS SCANNED FOR EACH
FILESPEC.  THE MATCH FILES  ARE  THEN  SORTED  IN  ORDER  OF
POSITION ON TAPE, AND DOUBLE ENTRIES REMOVED.  THE TAPE THEN
MOVES FORWARD AND COPIES THE INDICATED FILES TO DISK.   THIS
PROCEDURE CAUSES THE FOLLOWING RESTRICTIONS TO BE IMPOSED:


     1.  ALL FILES MUST GO TO THE SAME STRUCTURE

     2.  TOO MANY DUPLICATE ENTRIES CANNOT BE PROCESSED


THIS MEANS THAT MTA:*.*,MTA:*.* CANNOT  BE  PROCESSED  SINCE
MAGGIE  DOES NOT HAVE SUFFICIENT CORE TO SORT THIS LIST.  IN
THE DISTRIBUTION VERSION, 500 FILES  ARE  ALLOWED  PER  TAPE
(500 ACTIVE FILES) AND 700 FILES MAXIMUM MAY BE SPECIFIED IN
ANY ONE COPY TO DISK COMMAND.




1.2.3  DELETE FROM TAPE - 

     THE DIRECTORY IS READ INTO CORE (IF NOT ALREADY  THERE)
AND  THE FILE ENTRIES MATCHING THE FILE SPECS ARE DELETED BY
ZEROING THE FIRST  WORD  OF  THAT  FILE'S  FIVE-WORD  BLOCK.
FILES ARE LISTED AS THEY ARE DELETED.




1.2.4  FORMAT TAPE COMMAND - 

     THE TAPE IS REWOUND.  A FULL DIRECTORY BLOCK  OF  ZEROS
IS  WRITTEN  AND THEN SIX INCHES OF BLANK TAPE.  THE TAPE IS
ONCE AGAIN REWOUND.




1.2.5  TAG COMMAND - 

     THE TAPE DIRECTORY IS READ INTO CORE AND THE TAPE LABEL
WRITTEN INTO THE SECOND WORD OF THE CORE DIRECTORY.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 5
GENERAL PHILOSOPHY


1.2.6  REWIND TAPE COMMAND - 

     THE TAPE IS REWOUND AND THE DIRECTORY IS  WRITTEN  BACK
ON  IF  IT HAS BEEN CHANGED SINCE RUNNING THE PROGRAM.  TAPE
IS LEFT AT LOAD-POINT.




1.2.7  EXIT COMMAND - 

     IF THE  CORE  DIRECTORY  HAS  BEEN  CHANGED  SINCE  THE
PROGRAM  WAS  RUN, A W COMMAND IS PREFORMED.  OTHERWISE, THE
PROGRAM EXITS.




1.2.8  "RECONSTRUCT" DIRECTORY COMMAND - 

     THE TAPE IS REWOUND, AND ALL HEADER FILES ARE READ INTO
THE  CORE  DIRECTORY.   FILES WHICH ARE SUPERSEEDED ARE ALSO
SUPERSEEDED IN THE CORE DIRECTORY.   FILE  WHICH  HAVE  BEEN
DELETED  BUT  NOT  SUPERSEEDED  ARE RE-ENTERED INTO THE TAPE
DIRECTORY.  IF A LARGE AMOUNT OF DELETING HAS BEEN DONE, THE
USER  MAY OVERFLOW THE DIRECTORY SPACE, AND GET A "DIRECTORY
FULL" ERROR.  THE CORE DIRECTORY MAY THEN  BE  WRITTEN  ONTO
TAPE WITH THE REWIND OR EXIT COMMANDS.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 6
INTRODUCTION


2.0  INTRODUCTION

     MAGGIE ALLOWS A USER TO USE A MAGTAPE IN A MANNER  MUCH
LIKE  A  DECTAPE.   FILES ARE CALLED BY NAME FROM THE TAPE'S
DIRECTORY IN A MANNER MUCH LIKE PIP.  THE  USER  CAN  DELETE
FILES,  ADD NEW FILES, ZERO THE DIRECTORY, AND COPY FILES TO
DISK OR DECTAPE.  IN ADDITION DIRECTORY LISTING AND  GARBAGE
COLLECTING  FROM  THE  TAPE  ARE  SUPPORTED.   THESE WILL BE
EXPLAINED IN DETAIL IN WHAT FOLLOWS.



2.1  COMMAND FORMAT

     TO ENGAGE MAGGIE, THE USER TYPES:

        .R MAGGIE
        -

AND MAGGIE RESPONDS:

        *

WHICH IS A PROMPT FOR USER INSTRUCTION.  A COMMAND MAY  THEN
BE  GIVEN  AS  A  DIRECT  COMMAND  OR A COMMAND STRING.  THE
DIRECT COMMANDS ARE:

        /E  TO EXIT TO MONITOR LEVEL
        /H  TO TYPE A SHORT HELP-TEXT
        /S  TO GIVE THE STATUS OF THE DIRECTORY IN CORE.

COMMAND STRINGS TAKE THE FORM:

        <DEV>:/<SWITCH>_<FILE SPECS>

WHERE <FILESPECS> TAKE THE FORM:

        <DEV>:<FILE>.<EXT>,<DEV>:<FILE>.<EXT>,...

THE SWITCHES ALLOWED WITHIN A COMMAND STRING ARE:

        /D DELETE FILES
        /F FORMAT THE TAPE (ZERO THE DIRECTORY)
        /L LIST THE TAPE DIRECTORY
        /M GIVE HARDWARE STATUS OF A PARTICULAT DRIVE
        /Q FAST FORM OF /L LISTING FILENAMES ONLY
        /R RECONSTRUCTS A DIRECTORY FROM HEADER-FILES
        /T LABELS A TAPE
        /W REWINDS THE TAPE AND WRITES THE DIRECTORY ON
        /X COPIES FILES

THE COMMANDS "R" AND "F" USE THE FOLOWING FORMAT:

        *MTA:/R_
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 7
INTRODUCTION


        *MTA:/F_

WHERE THE RIGHT HAND SIDE IS IGNORED SINCE IT IS NOT NEEDED.
NOTE THAT THE CHARACTERS "=" AND "_" ARE INTERCHANGIBLE WITH
MAGGIE.




2.1.1  DELETE COMMAND - 

     THIS  COMMANDS  DELETES   A   FILE   ENTRY   FROM   THE
IN-CORE-DIRECTORY (NOT FROM THE TAPE) AND RETURNS TO COMMAND
LEVEL.  THE PHYSICAL TAPE  IS  NEVER  ALTERED  BY  A  DELETE
COMMAND.   AFTER  A  DELETE  COMMAND,  THE DIRECTORY MUST BE
WRITTEN BACK ON THE TAPE TO MAKE IT EFFECTIVE  (SEE  /E  AND
/W).  FOR EXAMPLE:

        *MTA0:/D_FOO.*,*.BAK,*.AB?

WILL DELETE ALL FILES NAMED FOO REGARDLESS OF EXTENSION, ALL
FILES  WITH EXTENSION OF ".BAK" REGARDLESS OF FILE NAME, AND
ALL FILES WHICH HAVE "A" AND "B" TOGETHER IN  THE  EXTENSION
REGARDLESS OF THE THIRD CHARACTER.  NOTE THAT THE SEQUENCE:

        *MTA:/D_FOOBAR

WILL DELETE ALL FILES WHICH HAVE A NULL EXTENSION.




2.1.2  FORMAT TAPE COMMAND - 

     THE /F COMMAND ZEROS THE TAPES DIRECTORY BLOCK (IF ANY)
AND  WRITES  A  NEW  DIRECTORY  OF ALL ZEROS FOLLOWED BY SIX
INCHES OF BLANK TAPE TO ALLOW FOR SPACING  OPERATIONS  WHICH
MAY    VARY    FROM    DRIVE   TO   DRIVE.    IN   SUCESSIVE
DIRECTORY-WRITES, ONLY  3  INCHES  OF  BLANK  TAPE  WILL  BE
WRITTEN,  AND  NO  EOF (SEE /W AND /E).  THE /F COMMAND DOES
NOT ALTER THE IN-CORE-DIRECTORY.  




2.1.3  LIST DIRECTORY COMMAND - 

     THE /L COMMAND LISTS IN ALPHEBETIZED ORDER,  THE  FILES
CORRESPONDING  TO  THE  GIVEN  FILE  SPECS.   THE  TAPE I.D.
TOGETHER WITH  DATE,  MODE,  PROTECTION,  SIZE,  AND  ACTUAL
POSITION  ON  TAPE  ARE  LISTED.   THE  SHORTER FORM OF THIS
COMMAND, /Q, LISTS ONLY TAPE ID AND FILENAMES.  FOR EXAMPLE:

        *TTY:/LMTA:*.*
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 8
INTRODUCTION


WILL LIST THE DIRECTORY OF THE ENTIRE TAPE ON THE TTY.   THE
COMMAND:

        *LPT:/LMTA:*.FOO

WILL LIST ALL FILES WITH EXTENSION FOO ON THE  LINE-PRINTER.
VALID  LISTING  DEVICES ARE DISK, DECTAPE, LINE-PRINTER, AND
TERMINAL.  MAGNETIC TAPE IS  NOT  A  VALID  LISTING  DEVICE.
WHERE  AN  ENTER  UUO IS MANDATORY FOR FILES (DISK, DECTAPE,
SPOOLED LPT), THE DIRECTORY FILE  WILL  BE  CALLED  <ID>.DIR
WHERE <ID> IS THE TAPE ID.  IF NO TAPE ID HAS BEEN GIVEN (BY
A /T COMMAND) THE NAME "MAGTAP.DIR" IS ASSUMED.




2.1.4  HARDWARE STATUS COMMAND (/M) - 

     THIS COMMAND PRODUCES A DESCRIPTION OF HARDWARE  DEVICE
ERRORS, NUMBER OF WORDS READ AND WRITTEN, THE TAPE'S REELID,
AND PHYSICAL TAPE POSITION.  LISTING  IS  TO  THE  TERMINAL.
THIS SEQUENCE:

        *MTA1:/M

WOULD LIST THE STATUS OF MTA DRIVE 1.  LOGICAL DEVICE  NAMES
MAY ALSO BE USED.  THE USER IS PERMITTED TO SPECIFY A DEVICE
WHICH HE DOES NOT PRESENTLY OWN.




2.1.5  RECONSTRUCT DIRECTORY COMMAND (/R) - 

     THIS COMMAND ALLOWS A  USER  TO  "RECONSTRUCT"  A  DEAD
DIRECTORY  FROM  THE  FILE HEADERS ON TAPE.  MAGGIE USES THE
FOLLOWING STRUCTURE FOR TAPE STORAGE:
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES             Page 9
INTRODUCTION


        -------------------------
        I                       I
        I  DIRECTORY BLOCK      I
        I                       I
        I.......................I
        I                       I
        I HEADER FILE # 1       I
        I                       I
        I.......................I
        I                       I
        I ACTUAL FILE  1        I
        I                       I
        I.......................I
        I                       I
        I  HEADER FILE #2       I
        I                       I
        I.......................I
        I                       I
                (ETC)

A HEADER FILE IS A  FIVE-WORD  FILE  ASSOCIATED  WITH  EVERY
ACTUAL  FILE  ON  THE  TAPE.   THE  HEADER  FILE  CONTAINS A
DIRECTORY ENTRY IN EXACTLY  THE  SAME  FORMAT  AS  THE  TAPE
DIRECTORY.   THESE HEADERS ARE USED ONLY TO RECONSTRUCT LOST
DIRECTORIES.  THE COMMAND FORMAT IS:

        *MTA0:/R_
        -

IF SUCCESSFUL, MAGGIE RESPONDS WITH THE  MESSAGE  "DIRECTORY
RECONSTRUCTED."


                            NOTE

               WHEN     RECONSTRUCTING      A
               DIRECTORY,   FILES  WHICH  HAD
               BEEN PREVIOUSLY  DELETED  WILL
               ONCE    AGAIN    BE   IN   THE
               DIRECTORY.  IF MANY FILES  HAD
               BEEN  DELETED,  THIS MAY CAUSE
               MAGGIE TO STORE MORE THAN  500
               FILES  IN  THE  DIRECTORY  AND
               GIVE A DIRECTORY FULL ERROR.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES            Page 10
INTRODUCTION


2.1.6  TAG COMMAND (/T) - 

     THIS COMMAND ALLOWS THE USER TO LABEL HIS TAPE WITH ANY
SIX CHARACTER ID.  THE FORM IS:

        *MTA:/T_LABEL
        -

WHERE  "LABEL"  IS  A  6  CHARACTER   IDENTIFICATION   CODE.
ALTHOUGH  ANY  CHARACTERS  IN SIXBIT CODE MAY BE USED, IT IS
ADVISIBLE TO AVOID NON-ALPHEBETIC AND NON-NUMERIC CHARACTERS
SINCE  DIRECTORIES PRINTED WITH THESE NAMES AS FILENAMES ARE
NOT RECOGNIZED BY ALL PDP-10 SOFTWARE.




2.1.7  REWIND TAPE (/W) - 

     THE /W COMMAND REWINDS THE SPECIFIED TAPE AND WRITES  A
FRESH  COPY  OF  THE  DIRECTORY FROM CORE TO TAPE (IF A COPY
EXISTS IN CORE).  NOTE THAT  MAGGIE  COMMANDS  POSITION  THE
TAPE  BY  THEMSELVES  AND  NEED NO EXTERNAL ASSISTANCE.  THE
FORM OF THIS COMMAND IS:

        *MTA:/W_
        -

WHERE MTA IS A PHYSICAL OR LOGICAL MAGNETIC TAPE NAME.




2.1.8  COPY FILES (/X) - 

     THIS COMMAND ALLOWS A USER TO COPY FILES FROM TAPE TO A
DEVICE AND FROM A DEVICE TO TAPE.  MAGGIE WILL NOT COPY FROM
DISK TO DISK OR  FROM  DECTAPE  TO  DISK.   ALL  COPYS  MUST
INVOLVE  A  MAGNETIC  TAPE AND A DIRECTORY DEVICE FOR OUTPUT
(DISK OR DTA).  THE FORM FOR THIS COMMAND IS:

        *<ODEV:/X_<IDEV:<FILE.EXT,<IDEV:<FILE.EXT...
        -

WHERE ODEV OS THE OUTPUT DEVICE;  IDEV IS THE INPUT  DEVICE;
AND  THE DEFAULT FOR IDEV IS "DSK."  WILDCARDS (* AND ?) ARE
PERMITTED IN FILE SPECS BUT NOT IN DEVICE SPECS.  IF IDEV IS
NOT  DSK, IT MUST BE STATED EXPLICITLY FOR EACH OCCURENCE IN
THE COMMAND STRING.

     ON A COPY FROM DISK TO TAPE, THE UFD FOR THAT DEVICE IS
SCANNED  AND  THE  FILES  ENTERED DIRECTLY.  FOR A COPY FROM
TAPE TO DISK, THE COMMAND LINE IS SCANNED AND THE FILES  ARE
RETREIVED  IN  THE  ORDER  IN WHICH THEY APPEAR ON THE TAPE.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES            Page 11
INTRODUCTION


THIS ELIMINATES EXCESSIVE REWINDING AND DOES NOT REQUIRE THE
USER TO KNOW THE POSITION OF A FILE ON TAPE AT ANY TIME.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES            Page 12
OVERALL SPECIFICATIONS


3.0  OVERALL SPECIFICATIONS

     AS DISTRIBUTED MAGGIE IS SPECIFIED AS FOLLOWS:

NAME                    MAGGIE.MAC
SOURCE LANGUAGE         MACRO-10
SIZE                    7+0 NON-REENTRANT
VERSION                 1A(1)
HARDWARE REQUIRED       MINIMUM 1 MAGTAPE DRIVE
SOFTWARE REQUIRED       NONE

IN ADDITION, THE FOLLOWING ASSEMBLY PARAMETERS ARE SET:

NFILES==^D500           MAX. NUMBER FILES IN DIRECTORY
MT.MOD==13              I/O MODE FOR COPY OPERATIONS
PDLEN==20               INTERNAL STACK LENGTH

MAGGIE HAS ALSO DEFINED 4 I/O CHANNELS  FOR  DISK,  MAGTAPE,
UFD SEARCHING, AND LISTING (CHANNELS 1-4).




3.1  DIRECTORY BLOCK STRUCTURE

     THE DIRECTORY BLOCK (SEE 1.1.5 FOR TAPE  STRUCTURE)  IS
FORMATTED AS FOLLOWS:

        -------------------------
        I   OF LAST FILE ON MTA I
        I.......................I
        I SIXBIT/TAPE LABEL/    I
        I.......................I
        I SIXBIT/FILENAME/      I
        I.......................I
        I SIXBIT/EXT/,,DATE     I
        I.......................I       (THIS IS THE
        I MODE,PROT,DATE2,TIME  I        STANDARD 
        I.......................I        4-WORD LOOKUP
        I       [P,PN]          I        BLOCK)
        I.......................I
        I (UNUSED),,POSITION    I
        I.......................I
        I                       I
        I       (ETC)           I
        I                       I
        -------------------------

WHERE THE STANDARD 4-WORD BLOCK IS SAVED FROM THE LOOKUP  OF
EACH  FILE, AND A FIFTH WORD ADDED TO DENOTE THE POSITION ON
THE TAPE.  THE POSITION IS ACTUALLY THE POSITION  IF  HEADER
FILES  ARE IGNORED, SO THAT THE FIRST FILE ON TAPE (POSITION
1) IS THE HEADER FILE FOR FILE #1.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES            Page 13
OVERALL SPECIFICATIONS


3.2  FILES ON THE TAPE--SPECIFICATIONS

     MAGGIE HAS BEEN TESTED WITH THE 5.07 MONITOR, AND THESE
SPECIFICATIONS APPLY:  

     1.   TAPE DENSITY IS 800 B.P.I

     2.   TAPE BLOCKSIZE IS 128 WORDS

     3.   FILES ARE WRITTEN IN IMAGE BINARY MODE (13)

     4.   ONE EOF FOLLOWS THE TAPE DIRECTORY

     5.   TWO EOF MARKS FOLLOW THE LAST PHYSICAL FILE ON
         TAPE

     6.   THE BLOCKSIZE MAY BE CHANGED USING "SET BLOCKSIZE"

NOTE THAT IF THE USER HAS  USED  THE  MONITOR  COMMAND  "SET
BLOCKSIZE"  TO  SET  THE  BUFFER  SIZE  ON ANY FILE, HE MUST
CONTINUE DOING THIS FOR THE ENTIRE  TAPE.   BLOCKSIZE  IS  A
PARAMETER SET AT MONGEN TIME AND IS INSTALLATION-DEPENDENT.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES            Page 14
GARBAGE COLLECTION


4.0  GARBAGE COLLECTION

     AT PRESENT (VERSION 1A(1)) GARBAGE COLLECTION  HAS  NOT
BEEN  IMPLIMENTED IN MAGGIE.  INSTED THE FOLLOWING PROCEDURE
MAY BE USED TO COMPACT ONTO ANOTHER TAPE:

        .MOUNT SCRATCH DISK
        -

        .R MAGGIE                       ;RUN MAGGIE
        -
        *MTA0:/F_                       ;USE MTA0 FOR 
        -
        *SCRATCH:/X_MTA1:*.*            ;COLLECTING NEW
        -
        *MTA0:/XSCRATCH:*.*             ;FILES FROM THE
        -                               ;SCRATCH DISK.
        *MTA0:/W_                       ;REWIND MTA0 AND
        -                               ;WRITE DRIECTORY.

GARBAGE COLLECTION WILL BE IMPLIMENTED IN THE  NEXT  RELEASE
OF MAGGIE.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES            Page 15
CREATION OF SAV FILE


5.0  CREATION OF SAV FILE

     THE FOLLOWING SEQUENCE WILL  MAKE  MAGGIE.SAV,  A  CREF
LISTING, AND REL FILE:

        .COMPIL MAGGIE.MAC/CREF
        -
        .CREF
        -
        .LOAD MAGGIE.REL
        -
        .SAVE
        -

MAGGIE WILL CONFORM TO THE AFORE MENTIONED SPECIFICATIONS.
MAGGIE--PSEUDO RANDOM-ACCESS FOR MAGTAPES            Page 16
MANTAINING MAGGIE


     MAGGIE WILL BE PERIODICALLY UPDATED  AND  RE-SUBMITTED.
USERS WHO EXPERIENCE PROBLEMS WITH THIS PROGRAM ARE ASKED TO
SUBMIT A DESCRIPTION OF THE  PROBLEM  ALONG  WITH  A  SAMPLE
PATCH IF POSSIBLE TO:

        JOHN L. MOSS
        FELDBERG COMPUTER CENTER
        BRANDEIS UNIVERSITY
        WALTHAM, MASS. 02154

THE PROBLEM WILL BE  CORRECTED  AS  SOON  AS  POSSIBLE,  AND
MAGGIE RE-RELEASED.

                       --DISCLAIMER--



                            NOTE

               THE SOFTWARE DESCRIBED  HEREIN
               IS  SUBJECT  TO CHANGE WITHOUT
               NOTICE.   NEITHER  THE  AUTHOR
               NOR BRANDEIS UNIVERSITY OR THE
               FELDBERG    COMPUTER    CENTER
               ASSUME  RESPONSIBILITY FOR THE
               USE  OR  RELIABILITY  OF  THIS
               PROGRAM.    IT   IS   STRONGLY
               RECOMMENDED  THAT  EACH   USER
               BECOME   THOROUGHLY   FAMILIAR
               WITH    THE    PROGRAM     AND
               DOCUMENTATION BEFORE USE.