Notes on relocatable autocoder

Pseudo ops:

  LC   #[,R[,x00[+/-#]]] Set current location counter.  R means relocatable.
                   Third operand controls century offset, and cannot appear
                   if re-setting to location counter with P not zero. A
                   location counter cannot be changed from relocatable to
                   nonrelocatable or vice-versa.

  LC   #,X,LABEL[+/-#]]  Set current location counter to LABEL.  Cannot
                   appear if re-setting to location counter with P not
                   zero.  LABEL shall be external.

  * in column 12   Defines label XXX for external use

.r file:

type :: R_file
  character(1) :: What   ! A to skip area of width FIELD(7:12) at ADR in LOC
                         ! C to clear field of width FIELD(7:12) at ADR in LOC
                         ! D for definition of LABEL as ADR in LOC
                         ! E for END to LABEL + ADR in LOC or ADR in LOC
                         ! F for a FIELD of LEN at ADR in LOC
                         ! L for org LC to LABEL
                         ! Q for A EQU B+Loc+ix and B is undefined,
                         !   or A is external is external; field might be %xx
                         ! R if ADR in LOC is a reference to LABEL with
                         !   offset FIELD(7:12) in decimal and index IX
                         ! X for EX or XFR to LABEL + ADR in LOC or ADR in LOC
                         ! 0 for org LC to X00+ADR
  character(6) :: Label
  character(5) :: Adr    ! Decimal address
  character(2) :: Loc    ! Location counter in decimal
  character(1) :: R      ! R if Adr in Loc needs relocation
  character(1) :: IX     ! Index in decimal, 0..3
  character(5) :: Line   ! Line number in source file
  character(2) :: Len    ! Length of field, might be zero if WM from DA
  character(52) :: Field ! Usually an instruction or DC/DCW/DSA contents
  character(1) :: WM     ! W If FIELD needs WM
  character(1) :: FR(2)  ! Starting positions in FIELD needing relocation, 1,2,5
  character(2) :: LCR(2) ! Location counters to use where FR is nonzero
  character(20) :: Text  ! Line(16:35) for output to tape
end type R_file

Control file:

<control> ::= <early>
              <segment> [ <segment> ... ]
              END [ label ]

<early> ::= ID [ deck_id ]

<early> ::= SKIP <number>
 skip this much in every block after the first one on the core file.

<segment> ::= <seg> <in> [ <in> ... ]

<seg> ::= SEG dname [ [+]<number> ]
 start relocatable location counters in segment at max of <number> or zero
 and one more than the maximum absolute address in the segment

<seg> ::= SEG dname -<number>
 end relocatable location counters in segment at <number>

<seg> ::= SEG dname *label
 start relocatable location counters in segment at label

<seg> ::= SEG dname rname [ rname... ]
 start relocatable location counters in segment at max of beginnings
 of segments rname [ rname ... ]

<seg> ::= SEG dname ( rname [ rname... ] )
 start segment relocatable location counters in after max of ends
 of segments rname [ rname ... ]

<in> ::= DATA file
 include data

<in> ::= SEQDATA file
 include data, and emit sequence numbers into columns 72-75, and the
 deck id into columns 76-80 if a "card deck" output is requested.  The
 deck id is emitted into columns 76-80 of tape records if Autocoder-format
 tape output is requested.

<in> ::= IN file [ file ... ]
 include specified .r files

Each of rname or label must appear in a previous segment.

Start the relocatable location counters in each file after the maximum of
the absolute ones, or the maximum of the relocatable location counters in
dependent segments.  Therefore, don't put relocatable location counters in
the same file with top-of-core absolute location counters!