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The m68k MRI assembler supports common sections which are merged by the linker.
Other object file formats do not support this.  <CODE>as</CODE> handles
common sections by treating them as a single common symbol.  It permits local
symbols to be defined within a common section, but it can not support global
symbols, since it has no way to describe them.

<LI>complex relocations

The MRI assemblers support relocations against a negated section address, and
relocations which combine the start addresses of two or more sections.  These
are not support by other object file formats.

<LI><CODE>END</CODE> pseudo-op specifying start address

The MRI <CODE>END</CODE> pseudo-op permits the specification of a start address.
This is not supported by other object file formats.  The start address may
instead be specified using the <CODE>-e</CODE> option to the linker, or in a linker
script.

<LI><CODE>IDNT</CODE>, <CODE>.ident</CODE> and <CODE>NAME</CODE> pseudo-ops

The MRI <CODE>IDNT</CODE>, <CODE>.ident</CODE> and <CODE>NAME</CODE> pseudo-ops assign a module
name to the output file.  This is not supported by other object file formats.

<LI><CODE>ORG</CODE> pseudo-op

The m68k MRI <CODE>ORG</CODE> pseudo-op begins an absolute section at a given
address.  This differs from the usual <CODE>as</CODE> <CODE>.org</CODE> pseudo-op,
which changes the location within the current section.  Absolute sections are
not supported by other object file formats.  The address of a section may be
assigned within a linker script.
</UL>

<P>
There are some other features of the MRI assembler which are not supported by
<CODE>as</CODE>, typically either because they are difficult or because they
seem of little consequence.  Some of these may be supported in future releases.

</P>

<UL>

<LI>EBCDIC strings

EBCDIC strings are not supported.

<LI>packed binary coded decimal

Packed binary coded decimal is not supported.  This means that the <CODE>DC.P</CODE>
and <CODE>DCB.P</CODE> pseudo-ops are not supported.

<LI><CODE>FEQU</CODE> pseudo-op

The m68k <CODE>FEQU</CODE> pseudo-op is not supported.

<LI><CODE>NOOBJ</CODE> pseudo-op

The m68k <CODE>NOOBJ</CODE> pseudo-op is not supported.

<LI><CODE>OPT</CODE> branch control options

The m68k <CODE>OPT</CODE> branch control options---<CODE>B</CODE>, <CODE>BRS</CODE>, <CODE>BRB</CODE>,
<CODE>BRL</CODE>, and <CODE>BRW</CODE>---are ignored.  <CODE>as</CODE> automatically
relaxes all branches, whether forward or backward, to an appropriate size, so
these options serve no purpose.

<LI><CODE>OPT</CODE> list control options

The following m68k <CODE>OPT</CODE> list control options are ignored: <CODE>C</CODE>,
<CODE>CEX</CODE>, <CODE>CL</CODE>, <CODE>CRE</CODE>, <CODE>E</CODE>, <CODE>G</CODE>, <CODE>I</CODE>, <CODE>M</CODE>,
<CODE>MEX</CODE>, <CODE>MC</CODE>, <CODE>MD</CODE>, <CODE>X</CODE>.

<LI>other <CODE>OPT</CODE> options

The following m68k <CODE>OPT</CODE> options are ignored: <CODE>NEST</CODE>, <CODE>O</CODE>,
<CODE>OLD</CODE>, <CODE>OP</CODE>, <CODE>P</CODE>, <CODE>PCO</CODE>, <CODE>PCR</CODE>, <CODE>PCS</CODE>, <CODE>R</CODE>.

<LI><CODE>OPT</CODE> <CODE>D</CODE> option is default

The m68k <CODE>OPT</CODE> <CODE>D</CODE> option is the default, unlike the MRI assembler.
<CODE>OPT NOD</CODE> may be used to turn it off.

<LI><CODE>XREF</CODE> pseudo-op.

The m68k <CODE>XREF</CODE> pseudo-op is ignored.

<LI><CODE>.debug</CODE> pseudo-op

The i960 <CODE>.debug</CODE> pseudo-op is not supported.

<LI><CODE>.extended</CODE> pseudo-op

The i960 <CODE>.extended</CODE> pseudo-op is not supported.

<LI><CODE>.list</CODE> pseudo-op.

The various options of the i960 <CODE>.list</CODE> pseudo-op are not supported.

<LI><CODE>.optimize</CODE> pseudo-op

The i960 <CODE>.optimize</CODE> pseudo-op is not supported.

<LI><CODE>.output</CODE> pseudo-op

The i960 <CODE>.output</CODE> pseudo-op is not supported.

<LI><CODE>.setreal</CODE> pseudo-op

The i960 <CODE>.setreal</CODE> pseudo-op is not supported.

</UL>



<H2><A NAME="SEC17" HREF="as_toc.html#TOC17">Name the Object File: <CODE>-o</CODE></A></H2>

<P>
<A NAME="IDX59"></A>
<A NAME="IDX60"></A>
<A NAME="IDX61"></A>
There is always one object file output when you run <CODE>as</CODE>.  By
default it has the name
<TT>`a.out'</TT> (or <TT>`b.out'</TT>, for Intel 960 targets only).
You use this option (which takes exactly one filename) to give the
object file a different name.

</P>
<P>
Whatever the object file is called, <CODE>as</CODE> overwrites any
existing file of the same name.

</P>


<H2><A NAME="SEC18" HREF="as_toc.html#TOC18">Join Data and Text Sections: <CODE>-R</CODE></A></H2>

<P>
<A NAME="IDX62"></A>
<A NAME="IDX63"></A>
<A NAME="IDX64"></A>
<A NAME="IDX65"></A>
<A NAME="IDX66"></A>
<CODE>-R</CODE> tells <CODE>as</CODE> to write the object file as if all
data-section data lives in the text section.  This is only done at
the very last moment:  your binary data are the same, but data
section parts are relocated differently.  The data section part of
your object file is zero bytes long because all its bytes are
appended to the text section.  (See section <A HREF="as.html#SEC37">Sections and Relocation</A>.)

</P>
<P>
When you specify <CODE>-R</CODE> it would be possible to generate shorter
address displacements (because we do not have to cross between text and
data section).  We refrain from doing this simply for compatibility with
older versions of <CODE>as</CODE>.  In future, <CODE>-R</CODE> may work this way.

</P>
<P>
When <CODE>as</CODE> is configured for COFF output,
this option is only useful if you use sections named <SAMP>`.text'</SAMP> and
<SAMP>`.data'</SAMP>.

</P>
<P>
<CODE>-R</CODE> is not supported for any of the HPPA targets.  Using
<CODE>-R</CODE> generates a warning from <CODE>as</CODE>.

</P>


<H2><A NAME="SEC19" HREF="as_toc.html#TOC19">Display Assembly Statistics: <CODE>--statistics</CODE></A></H2>

<P>
<A NAME="IDX67"></A>
<A NAME="IDX68"></A>
<A NAME="IDX69"></A>
<A NAME="IDX70"></A>
Use <SAMP>`--statistics'</SAMP> to display two statistics about the resources used by
<CODE>as</CODE>: the maximum amount of space allocated during the assembly
(in bytes), and the total execution time taken for the assembly (in CPU
seconds).

</P>


<H2><A NAME="SEC20" HREF="as_toc.html#TOC20">Announce Version: <CODE>-v</CODE></A></H2>

<P>
<A NAME="IDX71"></A>
<A NAME="IDX72"></A>
<A NAME="IDX73"></A>
<A NAME="IDX74"></A>
You can find out what version of as is running by including the
option <SAMP>`-v'</SAMP> (which you can also spell as <SAMP>`-version'</SAMP>) on the
command line.

</P>


<H2><A NAME="SEC21" HREF="as_toc.html#TOC21">Suppress Warnings: <CODE>-W</CODE></A></H2>

<P>
<A NAME="IDX75"></A>
<A NAME="IDX76"></A>
<A NAME="IDX77"></A>
<CODE>as</CODE> should never give a warning or error message when
assembling compiler output.  But programs written by people often
cause <CODE>as</CODE> to give a warning that a particular assumption was
made.  All such warnings are directed to the standard error file.
If you use this option, no warnings are issued.  This option only
affects the warning messages: it does not change any particular of how
<CODE>as</CODE> assembles your file.  Errors, which stop the assembly, are
still reported.

</P>


<H2><A NAME="SEC22" HREF="as_toc.html#TOC22">Generate Object File in Spite of Errors: <CODE>-Z</CODE></A></H2>
<P>
<A NAME="IDX78"></A>
<A NAME="IDX79"></A>
After an error message, <CODE>as</CODE> normally produces no output.  If for
some reason you are interested in object file output even after
<CODE>as</CODE> gives an error message on your program, use the <SAMP>`-Z'</SAMP>
option.  If there are any errors, <CODE>as</CODE> continues anyways, and
writes an object file after a final warning message of the form <SAMP>`<VAR>n</VAR>
errors, <VAR>m</VAR> warnings, generating bad object file.'</SAMP>

</P>


<H1><A NAME="SEC23" HREF="as_toc.html#TOC23">Syntax</A></H1>

<P>
<A NAME="IDX80"></A>
<A NAME="IDX81"></A>
This chapter describes the machine-independent syntax allowed in a
source file.  <CODE>as</CODE> syntax is similar to what many other
assemblers use; it is inspired by the BSD 4.2
assembler.

</P>



<H2><A NAME="SEC24" HREF="as_toc.html#TOC24">Preprocessing</A></H2>

<P>
<A NAME="IDX82"></A>
The <CODE>as</CODE> internal preprocessor:

<UL>
<LI>

<A NAME="IDX83"></A>
 
adjusts and removes extra whitespace.  It leaves one space or tab before
the keywords on a line, and turns any other whitespace on the line into
a single space.

<A NAME="IDX84"></A>
<LI>

removes all comments, replacing them with a single space, or an
appropriate number of newlines.

<A NAME="IDX85"></A>
<LI>

converts character constants into the appropriate numeric values.
</UL>

<P>
It does not do macro processing, include file handling, or
anything else you may get from your C compiler's preprocessor.  You can
do include file processing with the <CODE>.include</CODE> directive
(see section <A HREF="as.html#SEC93"><CODE>.include "<VAR>file</CODE>"</VAR></A>).  You can use the GNU C compiler driver
to get other "CPP" style preprocessing, by giving the input file a
<SAMP>`.S'</SAMP> suffix.  See section `Options Controlling the Kind of Output' in <CITE>Using GNU CC</CITE>.

</P>
<P>
Excess whitespace, comments, and character constants
cannot be used in the portions of the input text that are not
preprocessed.

</P>
<P>
<A NAME="IDX86"></A>
<A NAME="IDX87"></A>
<A NAME="IDX88"></A>
<A NAME="IDX89"></A>
If the first line of an input file is <CODE>#NO_APP</CODE> or if you use the
<SAMP>`-f'</SAMP> option, whitespace and comments are not removed from the input file.
Within an input file, you can ask for whitespace and comment removal in
specific portions of the by putting a line that says <CODE>#APP</CODE> before the
text that may contain whitespace or comments, and putting a line that says
<CODE>#NO_APP</CODE> after this text.  This feature is mainly intend to support
<CODE>asm</CODE> statements in compilers whose output is otherwise free of comments
and whitespace.

</P>


<H2><A NAME="SEC25" HREF="as_toc.html#TOC25">Whitespace</A></H2>

<P>
<A NAME="IDX90"></A>
<EM>Whitespace</EM> is one or more blanks or tabs, in any order.
Whitespace is used to separate symbols, and to make programs neater for
people to read.  Unless within character constants
(see section <A HREF="as.html#SEC30">Character Constants</A>), any whitespace means the same
as exactly one space.

</P>


<H2><A NAME="SEC26" HREF="as_toc.html#TOC26">Comments</A></H2>

<P>
<A NAME="IDX91"></A>
There are two ways of rendering comments to <CODE>as</CODE>.  In both
cases the comment is equivalent to one space.

</P>
<P>
Anything from <SAMP>`/*'</SAMP> through the next <SAMP>`*/'</SAMP> is a comment.
This means you may not nest these comments.

</P>

<PRE>
/*
  The only way to include a newline ('\n') in a comment
  is to use this sort of comment.
*/

/* This sort of comment does not nest. */
</PRE>

<P>
<A NAME="IDX92"></A>
Anything from the <EM>line comment</EM> character to the next newline
is considered a comment and is ignored.  The line comment character is
<SAMP>`#'</SAMP> on the i960;
<SAMP>`!'</SAMP> on the SPARC;
<SAMP>`;'</SAMP> for the HPPA;
<SAMP>`!'</SAMP> for the Z8000;
see section <A HREF="as.html#SEC128">Machine Dependent Features</A>.  
</P>
<P>
On some machines there are two different line comment characters.  One
character only begins a comment if it is the first non-whitespace character on
a line, while the other always begins a comment.

</P>
<P>
<A NAME="IDX93"></A>
<A NAME="IDX94"></A>
<A NAME="IDX95"></A>
To be compatible with past assemblers, lines that begin with <SAMP>`#'</SAMP> have a
special interpretation.  Following the <SAMP>`#'</SAMP> should be an absolute
expression (see section <A HREF="as.html#SEC58">Expressions</A>): the logical line number of the <EM>next</EM>
line.  Then a string (see section <A HREF="as.html#SEC31">Strings</A>) is allowed: if present it is a
new logical file name.  The rest of the line, if any, should be whitespace.

</P>
<P>
If the first non-whitespace characters on the line are not numeric,
the line is ignored.  (Just like a comment.)

</P>

<PRE>
                          # This is an ordinary comment.
# 42-6 "new_file_name"    # New logical file name
                          # This is logical line # 36.
</PRE>

<P>
This feature is deprecated, and may disappear from future versions
of <CODE>as</CODE>.

</P>


<H2><A NAME="SEC27" HREF="as_toc.html#TOC27">Symbols</A></H2>

<P>
<A NAME="IDX96"></A>
A <EM>symbol</EM> is one or more characters chosen from the set of all
letters (both upper and lower case), digits and the three characters
<SAMP>`_.$'</SAMP>.
On most machines, you can also use <CODE>$</CODE> in symbol names; exceptions
are noted in section <A HREF="as.html#SEC128">Machine Dependent Features</A>.
No symbol may begin with a digit.  Case is significant.
There is no length limit: all characters are significant.  Symbols are
delimited by characters not in that set, or by the beginning of a file
(since the source program must end with a newline, the end of a file is
not a possible symbol delimiter).  See section <A HREF="as.html#SEC43">Symbols</A>.
<A NAME="IDX97"></A>

</P>


<H2><A NAME="SEC28" HREF="as_toc.html#TOC28">Statements</A></H2>

<P>
<A NAME="IDX98"></A>
<A NAME="IDX99"></A>
<A NAME="IDX100"></A>
A <EM>statement</EM> ends at a newline character (<SAMP>`\n'</SAMP>) or an exclamation 
point (<SAMP>`!'</SAMP>).  The newline or exclamation point is considered part of the
preceding statement.  Newlines and exclamation points within character