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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><!-- Conditional Assembly --><HTML><HEAD><TITLE>Conditional Assembly</TITLE></HEAD><BODY BACKGROUND="spiral.gif" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#990099" ALINK="#FF0000"><TABLE WIDTH="98%"><TR><TD WIDTH=60 VALIGN=BOTTOM NOWRAP><IMG SRC="transp.gif" ALT="" WIDTH=60 HEIGHT=20></TD><TD><!-- Ab hier Seitentext: --><BIG><BR><P><STRONG><U>III.10 Conditional Assembly</U></STRONG></P><P>Conditional assembly allows to assemble or ignore selected parts of code.This can be used to keep the code for various program variants in a singlesource, to ease configuration control and maintenance. Conditional assemblyis also useful to write fancy macros.<BR>The following fourteen meta instructions have been implemented:</P><P><BLOCKQUOTE><STRONG><PRE>IF <expr> ELSEIF <expr>IFN <expr> ELSEIFN <expr>IFDEF <symbol> ELSEIFDEF <symbol>IFNDEF <symbol> ELSEIFNDEF <symbol>IFB <literal> ELSEIFB <literal>IFNB <literal> ELSEIFNB <literal>ENDIF ELSE</PRE></STRONG></BLOCKQUOTE></P><P>Meta instructions overlay the Intel <NOBR>MCS-51</NOBR> assembly language, butare not part of it! C programmers may compare them to C preprocessor commands.<BR>In the subsequent text, IFxx is used as a collective name for theIF/IFN/IFDEF/IFNDEF/IFB/IFNB instructions. In analogy ELSEIFxx is used as acollective name for the ELSEIF/ELSEIFN/ELSEIFDEF/ELSEIFNDEF/ELSEIFB/ELSEIFNBinstructions (not including ELSE).</P><P><OL TYPE=1><LI><A HREF="genifxx.htm">General IFxx Construction</A></LI><LI><A HREF="ifxxcon.htm">IFxx and ELSEIFxx Instructions</A></LI></OL></P></BIG><!-- Seitentext Ende --><P><BR><BR><CENTER><TABLE WIDTH="70%"><TR><TH><A HREF="contents.htm"><IMG SRC="home.gif" ALT="[contents]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="language.htm"><IMG SRC="up.gif" ALT="[up]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="predef.htm"><IMG SRC="back.gif" ALT="[back]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="genifxx.htm"><IMG SRC="next.gif" ALT="[next]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH></TR></TABLE></CENTER></P></TD></TR></TABLE></BODY></HTML>⌨️ 快捷键说明
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