MACN11 is a PDP-11 MACRO language assembler  which  operates
     on the PDP-10.  This document describes version 3 of MACN11; with
     the exception of differences listed in the following pages, it is
     compatible  with  the  language  accepted  by  MACRO-11 under DOS
     Version 9, as  described  in  DEC's  DOS/BATCH  assembler  manual
     (order no.  DEC-11-LASMA-A-D).

          Bug reports, comments,  and  suggestions  concerning  either
     version of MACN11 are welcome via net mail to Raveling@ISIB.

	Notes on MACN11 Version 3                          Page   2



  	--------  Language Variations from MACRO-11  ---------



             <<  Features not yet supported  >>


          .PSECT          -- Not recognized at present.
          .DSABL    REG  -- Parsed properly but ignored;
                    Register definitions are always enabled
                    at present.


               Both of these features will be supported in version 4.





               << Differences in defaults >>


          Default  modes  for  the  .LIST/.NLIST   and   .ENABL/.DSABL
          directives  can be changed by assembly parameters in MACN11.
          In the configuration maintained by ISI these defaults  match
          MACRO-11's except for the following:

               .NLIST    TTM  ; [format listings for lpt output]
               .ENABL    LC   ; [don't fold lower case]




	Notes on MACN11 Version 3                          Page   3



                <<  Language extensions  >>


     .ASCII & .ASCIZ 

          MACN11 allows multiple expressions, rather  than  just  one,
          within  brackets.   Expressions  are  delimited  by  commas.
          E.g., "<cr><lf>" can be written as "<cr,lf>".


     .ENABL & .DSABL

          These verbs recognize two nonstandard operands:

          NSF (Nonstandard features): Enabled by default.
               Enabling NSF allows use of MACN11's extended  features.
               Disabling  limits  the  acceptable  source  language to
               being strictly compatible with MACRO-11.

          ISD (Internal Symbol Definitions): Disabled by default
               Enabling ISD includes definitions of internal  symbols,
               as well as global symbols, in the object module output.
               These definitions allow generation of  a  symbol  table
               for debuggers such as DDT-11.

          HOV (Hexadecimal override): Disabled  by  default.   If  the
               current  radix  is 16 and HOV is enabled, then terms of
               expressions which begin with A-F are assumed to be  hex
               numbers, rather than symbols.  E.g.,

                    .ENABL    HOV ; Enabling hex override causes
                    MOV   A,R0 ; this instruction to load 10. into
                              ; R0, rather than the address of a
                              ; word labelled A.


     .ENDM 

          Interior macro definitions within a nest can  be  terminated
          by  a  .ENDM  whose  operand  is  the  name  of  an exterior
          definition.


     Hexadecimal numbers

          Hex numbers, using the digits 0-9 and A-F, may be  used  via
          extensions  of the existing radix control functions.  .RADIX
          accepts 16 as a valid operand to  set  the  current  default
          radix,  and temporary radix control includes "H" in addition
          to the standard "D", "O", and "B".

          When using hexadecimal as the default radix it  is  normally
          necessary  to  prefix  numbers  beginning  with  A-F by a 0;

	Notes on MACN11 Version 3                          Page   4



          otherwise they would be parsed as symbols.   Use  of  .ENABL
          HOV  eliminates  this  need  at  the  cost of making symbols
          beginning with A-F inaccessible.


     Logical shift operator ("_")

          An additional binary operator is  recognized  in  expression
          evaluation.   "a_b"  is evaluated as "the value of a shifted
          left b bits".  If b is negative, the term is shifted  right.
          Both  a  and  b may be any valid term, including a bracketed
          expression.

          A common use for  this  operator  is  in  defining  symbolic
          values  for  bit masks.  For example, "INTENA = 1_6" defines
          an interrupt enable mask as a 1 in bit 6.


     .PDP10

          The ".PDP10" directive is recognized, but is ignored.   This
          is for the sake of assembling Bliss-11 compiler output.



     Predefined symbols

          Symbols can be predefined by assembling their  symbol  table
          entries  into MACN11.  At present register names (R0-R7, SP,
          and PC) and ".MACN." are defined in this  way.   .MACN.   is
          equated to the assembler's version number.


     Radix 50 terms in expressions: ^R

          "^R" is recognized  as  a  unary  operator  in  expressions,
          indicating   that  the  next  three  characters  are  to  be
          converted to radix 50 format for use as a 16-bit value.  Any
          character  without  a  radix  50  equivalent is treated as a
          delimiter, and is taken as equivalent to trailing blanks  in
          evaluating the term.


     .SBHED 

          A  new  directive,  .SBHED,  specifies  a   subheading;   it
          functions  as  a conditional .PAGE followed by a .SBTTL.  It
          skips to a new page unless the most  recent  listing  output
          was  a  page  skip,  then  outputs  a standard page heading.
          .SBHED's operand field is included in the table of  contents
          and in all page subheadings until another .SBHED or a .SBTTL
          is issued.  The .SBHED directive itself is  the  first  line
          listed below the new page heading.

	Notes on MACN11 Version 3                          Page   5



	----------------  Operating  Procedures  -----------------



          Operating  procedures  for  MACN11  version  3  are   nearly
     identical to MACRO-11's.  The only differences are the following:

          "=" and "_" are accepted as synonyms for "<".
          The /PA switch is accepted but is ignored.
          An additional switch, /FO, is available to specify
               the PDP-10 file format for object output.
          Cross references are pretty disgusting.

          Details of these differences are included in the description
     below.




          MACN11  assembles  one  or  more  source   files,   normally
     producing  two files: a relocatable object module and an assembly
     listing.  Command string syntax is similar to MACRO-11's.

          Object files normally are generated in packed  format,  with
     each  PDP-11  word  right-adjusted  in  a  PDP-10 halfword.  This
     format is standard for other utilities which may deal with  these
     files (LNKX11, LINK11, FILEX, etc.).


     Command Input String


          When MACN11 is ready for a command it  lists  its  name  and
     version  number  on  the user's terminal, then outputs a "*" on a
     new line.  In return it expects the following sort of string:


     object,listing<source1,source2,...,sourcen


     "<" separates output file specifications from input  specs.   "="
          and "_" are equally acceptable.

          Each field in the command string specifies a file  name  and
          may  include  optional switches.  File names must conform to
          DEC  conventions  (6-byte   file   name,   optional   3-byte
          extension).   If  the  extension is omitted on any file name
          the assembler chooses a suitable default.

          A PPN (project-programmer  number)  may  be  supplied  where
          MACRO-11  would  accept  a  UIC  (user identification code).
          Under Tenex this is treated as a directory number.  MACN11's
          source  contains  assembly  parameters to allow it to accept

	Notes on MACN11 Version 3                          Page   6



          PPNs in the formats used by CMU and Stanford.


     Object is normally a relocatable object module  file,  ready  for
          input  to  LNKX11  or  LINK-11.   Its  default  extension is
          ".OBJ".  Absolute  binary  output,  with  default  extension
          ".BIN", can be generated by using ".ENABL ABS" in the source
          program, or by including a "/EN:ABS" switch in  the  command
          string.

          Object file format may be specified with the  "/FO"  switch.
          "/FO:P"  generates  packed  output (1 PDP-11 word per PDP-10
          halfword), and is the default.   "/FO:I"  forces  image-mode
          output, with one 8-bit byte per PDP-10 word.


     Listing is an ASCII file with  a  default  extension  of  ".LST".
          Cross  references  may  be obtained by using a "/CRF" switch
          with the listing file; this generates a file with  extension
          ".CRF",  which  must  be  run  through  CREF.  The resulting
          listing is terrible.  It looks a little better if  "/NL:SEQ"
          is  also  specified,  but  that doesn't cure the readability
          problems.  In addition, not all references  to  symbols  are
          recorded  in the cross reference.  All of these woes will be
          fixed by moving cross reference processing into MACN11; this
          will be done no later than version 5 of the assembler.


     Source files are in ASCII, with the following default  extensions
          recognized by the assembler:

               ".M11", ".P11", ".MAC", blank


          Either the object file or the listing file,  but  not  both,
     may  be  omitted.   Any  number of source files (except 0) may be
     used.

	Notes on MACN11 Version 3                          Page   7



-------------  Assembler Generation Options  --------------



          The  source  for  MACN11  contains  a  number  of   assembly
     parameters  to allow customizing it for individual installations.
     Most, but not all,  are  clustered  on  a  couple  pages  at  the
     beginning.  The most useful of these parameters, and their values
     in the ISI source, are .  .  .


      Name           Default Value    Meaning
     --------        -----------     ---------------------------------

     CCLSW               0           1 => Generate CCL support

     CMUSW               0           1 => Handle CMU PPNs
                                          in file names

     STANSW              0           1 => Handle Stanford PPNs

     PAGSIZ           D54            Number of lines per page
                                     on listing output

     ENDEF   LCFLG+PNCFLG+REGFLG     Default .ENABL modes; bit names
                                     are "xxxFLG", where "xxx" is an
                                     operand of .ENABL/.DSABL.

     LDEF  777777-LLD-LME-LMEB-LTTM  Default .LIST modes; bit names
                                     are "Lxxx", where "xxx" is an
                                     operand of .LIST/.NLIST.



          Additional symbols can be  predefined  by  assembling  their
     definitions  into  the  prototype  symbol  table  which begins at
     location PERMST, near the end of the  assembly.   This  table  is
     kept  in  ascending  order  by  the  .RAD50 (mod 40) value of the
     symbol, which is equivalent to alphabetic order  except  for  "."
     and "$".  Entry format is .  .  .

             XWD                     ; type-flags,value
             GENM40  N,A,M,E     ; 1-6 characters

     Type flags may be .  .  .

     DEFSYM  -- Symbol is defined
     REGSYM  -- Symbol identifies a register
     GLBSYM  -- Symbol is global (external if DEFSYM not set)

	Notes on MACN11 Version 3                          Page   8



     ---------  Internal Symbol Definitions  ----------



             When ISD is enabled, internal symbol  definition  entries
     When  .ENABL ISD is in effect, internal symbol definition entries
     are included in  the  generated  object  module's  global  symbol
     dictionary.   These  are type 2 GSD entries, which are identified
     in appendix B (B.1.3) of  the  DOS/Batch  Linker  manual.   Their
     format is:


             ---------------------------------
             !            Symbol             !
             !             Name              !
             ---------------------------------
             !      2        !     Flags     !
             ---------------------------------
             !            Value              !
             ---------------------------------


     The symbol name is two words in .RAD50 format.

     The flag byte currently has only one bit defined: Bit 0 is set if
     the symbol is a register name.  All undefined bits are set to 0.

     The value is identical to that field in global symbol name  (type
     4) entries: It is the symbol's offset from the start of the csect
     identified by the most recent type 1  (csect  name)  entry.   ISD
     values  are  absolute  if they follow the absolute csect's type 1
     entry.î