mirror of
https://github.com/michaelcmartin/Ophis.git
synced 2024-11-19 18:33:33 +00:00
178 lines
2.8 KiB
HTML
178 lines
2.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<HTML
|
|
><HEAD
|
|
><TITLE
|
|
>16-bit comparisons</TITLE
|
|
><META
|
|
NAME="GENERATOR"
|
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
|
|
REL="HOME"
|
|
TITLE="Programming with Ophis"
|
|
HREF="book1.html"><LINK
|
|
REL="UP"
|
|
TITLE="The Second Step"
|
|
HREF="c486.html"><LINK
|
|
REL="PREVIOUS"
|
|
TITLE="16-bit addition and subtraction"
|
|
HREF="x527.html"><LINK
|
|
REL="NEXT"
|
|
TITLE="Structured Programming"
|
|
HREF="c543.html"></HEAD
|
|
><BODY
|
|
CLASS="SECTION"
|
|
BGCOLOR="#FFFFFF"
|
|
TEXT="#000000"
|
|
LINK="#0000FF"
|
|
VLINK="#840084"
|
|
ALINK="#0000FF"
|
|
><DIV
|
|
CLASS="NAVHEADER"
|
|
><TABLE
|
|
SUMMARY="Header navigation table"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
CELLPADDING="0"
|
|
CELLSPACING="0"
|
|
><TR
|
|
><TH
|
|
COLSPAN="3"
|
|
ALIGN="center"
|
|
>Programming with Ophis</TH
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="10%"
|
|
ALIGN="left"
|
|
VALIGN="bottom"
|
|
><A
|
|
HREF="x527.html"
|
|
ACCESSKEY="P"
|
|
><<< Previous</A
|
|
></TD
|
|
><TD
|
|
WIDTH="80%"
|
|
ALIGN="center"
|
|
VALIGN="bottom"
|
|
>The Second Step</TD
|
|
><TD
|
|
WIDTH="10%"
|
|
ALIGN="right"
|
|
VALIGN="bottom"
|
|
><A
|
|
HREF="c543.html"
|
|
ACCESSKEY="N"
|
|
>Next >>></A
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><HR
|
|
ALIGN="LEFT"
|
|
WIDTH="100%"></DIV
|
|
><DIV
|
|
CLASS="SECTION"
|
|
><H1
|
|
CLASS="SECTION"
|
|
><A
|
|
NAME="AEN537"
|
|
>16-bit comparisons</A
|
|
></H1
|
|
><P
|
|
> Doing comparisons on extended precision values is about the same
|
|
as doing them on 8-bit values, but you have to have the value you
|
|
test in memory, since it won't fit in the accumulator all at once.
|
|
You don't have to store the values back anywhere, either, since
|
|
all you care about is the final state of the flags. For example,
|
|
here's a signed comparison, branching to <TT
|
|
CLASS="LITERAL"
|
|
>label</TT
|
|
>
|
|
if the value in $C100-1 is less than 1000 ($03E8):
|
|
</P
|
|
><TABLE
|
|
BORDER="0"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="100%"
|
|
><TR
|
|
><TD
|
|
><PRE
|
|
CLASS="PROGRAMLISTING"
|
|
> SEC
|
|
LDA $C100
|
|
SBC #$E8
|
|
LDA $C101 ; We only need the carry bit from that subtract
|
|
SBC #$03
|
|
BMI label</PRE
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><P
|
|
> All the commentary on signed and unsigned compares holds for
|
|
16-bit (or higher) integers just as it does for the 8-bit
|
|
ones.
|
|
</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="NAVFOOTER"
|
|
><HR
|
|
ALIGN="LEFT"
|
|
WIDTH="100%"><TABLE
|
|
SUMMARY="Footer navigation table"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
CELLPADDING="0"
|
|
CELLSPACING="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="x527.html"
|
|
ACCESSKEY="P"
|
|
><<< Previous</A
|
|
></TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="book1.html"
|
|
ACCESSKEY="H"
|
|
>Home</A
|
|
></TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="c543.html"
|
|
ACCESSKEY="N"
|
|
>Next >>></A
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
>16-bit addition and subtraction</TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="c486.html"
|
|
ACCESSKEY="U"
|
|
>Up</A
|
|
></TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
>Structured Programming</TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></BODY
|
|
></HTML
|
|
> |