mirror of
https://github.com/michaelcmartin/Ophis.git
synced 2024-07-02 10:29:30 +00:00
197 lines
3.0 KiB
HTML
197 lines
3.0 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<HTML
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><HEAD
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><TITLE
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>Writing the actual code</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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REL="HOME"
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TITLE="Programming with Ophis"
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HREF="book1.html"><LINK
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REL="UP"
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TITLE="The basics"
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HREF="c35.html"><LINK
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REL="PREVIOUS"
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TITLE="Related commands and options"
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HREF="x119.html"><LINK
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REL="NEXT"
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TITLE="Assembling the code"
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HREF="x149.html"></HEAD
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><BODY
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CLASS="SECTION"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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SUMMARY="Header navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Programming with Ophis</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="x119.html"
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ACCESSKEY="P"
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><<< Previous</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>The basics</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="x149.html"
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ACCESSKEY="N"
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>Next >>></A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECTION"
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><H1
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CLASS="SECTION"
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><A
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NAME="AEN140"
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>Writing the actual code</A
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></H1
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><P
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> Now that we have our header information, let's actually write
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the <SPAN
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CLASS="QUOTE"
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>"Hello world"</SPAN
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> program. It's pretty
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short—a simple loop that steps through a hardcoded array
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until it reaches a 0 or outputs 256 characters. It then returns
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control to BASIC with an <TT
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CLASS="LITERAL"
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>RTS</TT
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> statement.
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</P
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><P
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> Each character in the array is passed as an argument to a
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subroutine at memory location $FFD2. This is part of the
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Commodore 64's BIOS software, which its development
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documentation calls the KERNAL. Location $FFD2 prints out the
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character corresponding to the character code in the
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accumulator.
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</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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> ldx #0
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loop: lda hello, x
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beq done
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jsr $ffd2
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inx
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bne loop
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done: rts
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hello: .byte "HELLO, WORLD!", 0
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</PRE
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></TD
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></TR
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></TABLE
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><P
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> The complete, final source is available in
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the <A
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HREF="a454.html#TUTOR1-SRC"
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><I
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><I
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>tutor1.oph</I
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></I
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></A
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> file.
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</P
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="x119.html"
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ACCESSKEY="P"
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><<< Previous</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="book1.html"
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ACCESSKEY="H"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="x149.html"
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ACCESSKEY="N"
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>Next >>></A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>Related commands and options</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="c35.html"
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ACCESSKEY="U"
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Assembling the code</TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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> |