<html lang="en"> <head> <title>PDP-11-Syntax - Using as</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="Using as"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="PDP_002d11_002dDependent.html#PDP_002d11_002dDependent" title="PDP-11-Dependent"> <link rel="prev" href="PDP_002d11_002dPseudos.html#PDP_002d11_002dPseudos" title="PDP-11-Pseudos"> <link rel="next" href="PDP_002d11_002dMnemonics.html#PDP_002d11_002dMnemonics" title="PDP-11-Mnemonics"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- This file documents the GNU Assembler "as". Copyright (C) 1991-2015 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''. --> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="PDP-11-Syntax"></a> <a name="PDP_002d11_002dSyntax"></a> <p> Next: <a rel="next" accesskey="n" href="PDP_002d11_002dMnemonics.html#PDP_002d11_002dMnemonics">PDP-11-Mnemonics</a>, Previous: <a rel="previous" accesskey="p" href="PDP_002d11_002dPseudos.html#PDP_002d11_002dPseudos">PDP-11-Pseudos</a>, Up: <a rel="up" accesskey="u" href="PDP_002d11_002dDependent.html#PDP_002d11_002dDependent">PDP-11-Dependent</a> <hr> </div> <h4 class="subsection">9.33.3 PDP-11 Assembly Language Syntax</h4> <p><a name="index-PDP_002d11-syntax-1797"></a> <a name="index-DEC-syntax-1798"></a><a name="index-BSD-syntax-1799"></a><code>as</code> supports both DEC syntax and BSD syntax. The only difference is that in DEC syntax, a <code>#</code> character is used to denote an immediate constants, while in BSD syntax the character for this purpose is <code>$</code>. <p><a name="index-PDP_002d11-general_002dpurpose-register-syntax-1800"></a>general-purpose registers are named <code>r0</code> through <code>r7</code>. Mnemonic alternatives for <code>r6</code> and <code>r7</code> are <code>sp</code> and <code>pc</code>, respectively. <p><a name="index-PDP_002d11-floating_002dpoint-register-syntax-1801"></a>Floating-point registers are named <code>ac0</code> through <code>ac3</code>, or alternatively <code>fr0</code> through <code>fr3</code>. <p><a name="index-PDP_002d11-comments-1802"></a>Comments are started with a <code>#</code> or a <code>/</code> character, and extend to the end of the line. (FIXME: clash with immediates?) <p><a name="index-PDP_002d11-line-separator-1803"></a>Multiple statements on the same line can be separated by the ‘<samp><span class="samp">;</span></samp>’ character. </body></html>