DOC: Cleaned up symbols keyboard example and provided a walk through
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michaelangel007
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1 changed files with 41 additions and 18 deletions
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@ -6,25 +6,48 @@
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</head>
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<body style="DIRECTION: ltr" lang="en-US">
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<h2><a name="Symbols"></a>Symbols</h2>
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<p>
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<p>
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When a programmer writes an assembly language program instead of directly referring to a memory address over and over again they use a <b>symbolic name</b> instead.
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For example, instead of always directly hard-coding $C000 everywhere to read the keyboard they would instead write:
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<p><font color="#00b8ff"><font face="courier"><b><pre style="background: rgb(0,0,0) 0% 50%;">
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KEYBOARD EQU $C000
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1 LDA KEYBOARD
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BPL 1
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</p>
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<p><font color="#00b8ff"><font face="courier"><b><pre style="background: rgb(0,0,0) 0% 50%;">
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ORG $300
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KEYBOARD EQU $C000
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300:AD 00 C0 .1 LDA KEYBOARD
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303:10 FB BPL .1
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305:8D 00 04 STA $0400
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306:60 RTS
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</pre></b></font></font></p>
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</p>When debugging assembly programs since you typically don't have the source file availabe you can tell the debugger how to interpret a memory address as a variable name or symbol.
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A <b>symbol</b> is the symbolic name and the address assigned to it.</P>
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<p>
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Let's try this out in the debugger. Make sure AppleWin is running. Press F2 (to reboot), then Ctrl-F2 (to break), and F7 (to enter the debugger.)
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If you don't want to type in the following hex code, you can select it, copy it (Ctrl-C), and paste it into the Debugger console (Ctrl-V).
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</p>
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<p><font color="#00b8ff"><font face="Courier"><b><pre style="BACKGROUND: rgb(0,0,0) 0% 50%;">
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300:AD 00 C0 10 FB 8D 00 04 60
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300L
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</pre></b></font></font></p>
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<p>
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Press F7 to exit the debugger, then type:
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</p>
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<p><font color="#00b8ff"><font face="Courier"><b><pre style="BACKGROUND: rgb(0,0,0) 0% 50%;">
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HOME:CALL 768
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</pre></b></font></font></p>
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<p>
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Press Enter. The emulated computer will wait for your to press a key and then echo it in the top left.
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</p>
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<p>
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When debugging assembly programs since you typically don't have the source file availabe you can tell the debugger how to interpret a memory address as a variable name or symbol.
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A <b>symbol</b> is the symbolic name and the address assigned to it.
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</p>
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<p>AppleWin supports loading of the assemblers ACME, and Merlin's symbol tables -- a collection of symbols, one per line, organized and collectively called a symbol table.
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The semi-colon is a comment-till-end-of-line. The file format per line is: <b>ADDRESS SYMBOL</b></p>
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<p>e.g.
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<p><font color="#00b8ff"><font face="courier"><b><pre style="background: rgb(0,0,0) 0% 50%;">
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<p>e.g.</p>
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<p><font color="#00b8ff"><font face="courier"><b><pre style="background: rgb(0,0,0) 0% 50%;">
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; IO Map
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C000 KEYBOARD
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</pre></b></font></font></p>
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<p>There are 9 symbol tables to help organize "modules"; each symbol table individually can be turned off/on independently.
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<p>
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There are <b>9</b> symbol tables to help organize "modules"; each symbol table individually can be turned off/on independently.
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<pre>
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MAIN APPLE2E.SYM
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BASIC A2_BASIC.SYM
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@ -37,11 +60,11 @@ C000 KEYBOARD
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PRODOS A2_PRODOS.SYM
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</pre></p>
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<p>On startup the debugger reads 3 symbol tables by default: Main, Basic, User1.</p>
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</p>
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</p>
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<p>Looking up symbols is easy. If you can't remember an address of a symbol,
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or the reversse -- can't remember the symbol for an address -- you can use the following symbol commands:
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(#### referes to either a hex address or a symbolic name)
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</p>
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(#### referes to either a hex address or a symbolic name)
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</p>
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<p><br>
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<br>
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</p>
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@ -60,10 +83,10 @@ C000 KEYBOARD
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</tr>
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<tr bgcolor="#cccccc">
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<td width="25%">
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<p><font color="#000000"><font face="Courier"><b><span style="BACKGROUND: 0% 50%; moz-background-clip: initial; moz-background-origin: initial; moz-background-inline-policy: initial">SYM</span></b></font></font></p>
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<p><font color="#000000"><font face="Courier"><b><span style="BACKGROUND: 0% 50%; ">SYM</span></b></font></font></p>
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</td>
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<td width="75%">
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<p><i><span style="BACKGROUND: 0% 50%; moz-background-clip: initial; moz-background-origin: initial; moz-background-inline-policy: initial">Display
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<p><i><span style="BACKGROUND: 0% 50%; ">Display
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the number of symbols in the Main, User, and Source symbol tables.</span></i></p>
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</td>
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</tr>
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@ -251,7 +274,7 @@ HOME</span></b></font></font></p>
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</tr>
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<tr bgcolor="#000000">
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<td bgcolor="#000000" width="276">
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<p><font color="#00b8ff"><font face="Courier"><b><span style="BACKGROUND: rgb(0,0,0) 0% 50%; moz-background-clip: initial; moz-background-origin: initial; moz-background-inline-policy: initial">SYM
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<p><font color="#00b8ff"><font face="Courier"><b><span style="BACKGROUND: rgb(0,0,0) 0% 50%;">SYM
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LIFE = 300</span></b></font></font></p>
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</td>
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<td bgcolor="#000000" width="515">
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@ -260,7 +283,7 @@ LIFE = 300</span></b></font></font></p>
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</tr>
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<tr bgcolor="#000000">
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<td bgcolor="#000000" width="276">
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<p><font color="#00b8ff"><font face="Courier"><b><span style="BACKGROUND: rgb(0,0,0) 0% 50%; moz-background-clip: initial; moz-background-origin: initial; moz-background-inline-policy: initial">E
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<p><font color="#00b8ff"><font face="Courier"><b><span style="BACKGROUND: rgb(0,0,0) 0% 50%;">E
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LIFE 64</span></b></font></font></p>
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</td>
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<td bgcolor="#000000" width="515">
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