! (c) copyright 1984 by the Vrije Universiteit, Amsterdam, The Netherlands.
! Explicit permission is hereby granted to universities to use or duplicate
! this program for educational or research purposes.  All other use or dup-
! lication  by universities,  and all use or duplication by other organiza-
! tions is expressly prohibited unless written permission has been obtained
! from the Vrije Universiteit. Requests for such permissions may be sent to

!      Dr. Andrew S. Tanenbaum
!      Wiskundig Seminarium
!      Vrije Universiteit
!      Postbox 7161
!      1007 MC Amsterdam
!      The Netherlands

! Organizations wishing to modify part of this software for subsequent sale
! must  explicitly  apply  for  permission.  The exact arrangements will be
! worked out on a case by case basis, but at a minimum will require the or-
! ganization to include the following notice in all software and documenta-
! tion based on our work:

!	    This product is based on the Pascal  system  developed  by
!      Andrew  S.  Tanenbaum, Johan W. Stevenson and Hans van Staveren
!      of the Vrije Universiteit, Amsterdam, The Netherlands.
!
!=========================================================================

! This is an interpreter for EM programs with no virtual memory for the
! the PMDS-II . This interpreter is adapted from an interpreter which was
! made for the pdp11 by Evert Wattel and Hans van Staveren . The present
! version is made by Freek van Schagen
!		     Vrije Universiteit
!		     Amsterdam.


!-------------------------------------------------------------------------

! The program requires preprocessing by the C-preprocessor . There are
! several options :
!	lword:  4byte word size in stead of 2 byte word size ;
!	test:   checking for undefined variables , nil pointers
!		array indices , overflow , etc ;
!	last:	generation of a file with the last 16 lines executed ;
!	count:	generation of a file with a flow count ;
!	flow:	generation of a file with a flow bitmap ;
!	prof:	generation of a file with a runtime profile ;
!	opfreq:	generation of a file with a frequency count per opcode.

!--------------------------------------------------------------------------

! Memory layout:

!  --------------------------------------------------------------------------
!  |		|	|     |		|	|	|	|	|   |
!  |	1	|   2	|  3  |	   4	|   5	|   6	|   	|   7	| 8 |
!  |		|	|     |		|	|	|	|	|   |
!  --------------------------------------------------------------------------

!	1:	Interpreter text+data+bss.
!	2:	EM text.
!	3:	EM procedure descriptors.
!	4:	EM global data area.
!	5:	tables for flow , count , profile.
!	6:	EM heap area.
!	7:	EM local data and stack.
!	8:	Arguments to the interpreter .


!REGISTER USE
!	pc	programcounter
!	a7=sp	stackpointer		d7	if lword: 1 , if not lword: 0
!	a6	external base= eb	d6	0
!	a5	scratch			d5	scratch
!	a4	address of loop		d4	scratch
!	a3	EM programcounter	d3	scratch
!	a2	local base =lb		d2	scratch
!	a1	address of return area	d1	scratch
!	a0	scratch			d0	opcode byte and scratch
