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BOOT.DOC
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1984-04-29
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2KB
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42 lines
***************************************************************************
** COPYRIGHT (C) MASSACHUSETTS INSTITUTE OF TECHNOLOGY AND HARVARD **
** UNIVERSITY, BIOMEDICAL ENGINEERING CENTER 1977. ALL RIGHTS RESERVED. **
***************************************************************************
THE STOIC BOOTSTRAP
J. SACHS 2/2/77
THE STOIC BOOTSTRAP IS A PROGRAM WHICH IS USED TO LOAD MEMORY
DIRECTLY FROM THE MASS STORAGE DEVICE. IT MAY BE USED TO BOOTSTRAP
COPIES OF STOIC OR ANY OTHER PROGRAM INTO MEMORY. THE ENTIRE
BOOTSTRAP RESIDES IS READ-ONLY MEMORY, BUT SOME RAM IS USED.
THE BOOTSTRAP FIRST SIZES MEMORY AND SETS THE STACK POINTER TO
THE TOP OF MEMORY. IT THEN TYPES THE MESSAGE "FILENAME ? "; TO
WHICH THE USER REPLIES BY TYPING A 1 TO 6 CHARACTER FILE NAME.
THE BOOTSTRAP THEN READS IN BLOCK 0 OF THE MASS STORAGE MEDIUM
(UNIT 0), I.E. THE DIRECTORY, AND SEARCHES FOR THE GIVEN FILENAME.
IF FOUND, THE FIRST BLOCK OF THE FILE IS READ INTO MEMORY. THIS
BLOCK CONTAINS THE INITIAL LOAD ADDRESS AND STARTING ADDRESS FOR
THE PROGRAM BEING LOADED. FINALLY, THE REMAINDER OF THE FILE IS
LOADED INTO MEMORY STARTING AT THE LOAD ADDRESS AND A BRANCH TO THE
STARTING ADDRESS IS MADE.
IF NOT FOUND, THE MESSAGE "FILENAME ? " IS GIVEN AGAIN AND ANOTHER
NAME MAY BE TYPED IN.
IF NO FILENAME IS GIVEN (BY RESPONDING WITH CARRIAGE RETURN TO THE
PROMPT MESSAGE), THE BOOTSTRAP JUMPS TO THE FIRST LOCATION OF RAM.
THIS FEATURE MAY BE USED TO INTERRUPT A PROGRAM WHICH IS RUNNING
BY PLACING AN APPROPRIATE JUMP IN THE FIRST LOCATION OF RAM.
IF A DISK ERROR OCCURS, THE MESSAGE "DISK ERROR" IS GIVEN, AND THE
BOOTSTRAP RESTARTS FROM THE BEGINNING.
***EOF***