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<a href='https://github.com/akkartik/mu/blob/main/linux/apps/ex4.subx'>https://github.com/akkartik/mu/blob/main/linux/apps/ex4.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Read a character from stdin, save it to a global, write it to stdout.</span>
<span id="L2" class="LineNr"> 2 </span><span class="subxComment">#</span>
<span id="L3" class="LineNr"> 3 </span><span class="subxComment"># To run:</span>
<span id="L4" class="LineNr"> 4 </span><span class="subxComment"># $ ./translate_subx 000init.subx apps/ex4.subx</span>
<span id="L5" class="LineNr"> 5 </span><span class="subxComment"># $ ./a.elf</span>
<span id="L6" class="LineNr"> 6 </span>
<span id="L7" class="LineNr"> 7 </span>== data
<span id="L8" class="LineNr"> 8 </span>
<span id="L9" class="LineNr"> 9 </span><span class="subxComment"># the global variable we save to</span>
<span id="L10" class="LineNr">10 </span><span class="SpecialChar">X</span>:
<span id="L11" class="LineNr">11 </span> 0/imm32 <span class="subxComment"># space for read() to write to</span>
<span id="L12" class="LineNr">12 </span>
<span id="L13" class="LineNr">13 </span>== code
<span id="L14" class="LineNr">14 </span>
<span id="L15" class="LineNr">15 </span><span class="SpecialChar">Entry</span>:
<span id="L16" class="LineNr">16 </span><span class="subxComment"># read(stdin, X, 1)</span>
<span id="L17" class="LineNr">17 </span><span class="subxS1Comment"># . fd = 0 (stdin)</span>
<span id="L18" class="LineNr">18 </span>bb/copy-to-ebx 0/imm32
<span id="L19" class="LineNr">19 </span><span class="subxS1Comment"># . data = X (location to write result to)</span>
<span id="L20" class="LineNr">20 </span>b9/copy-to-ecx <span class="SpecialChar"><a href='ex4.subx.html#L10'>X</a></span>/imm32
<span id="L21" class="LineNr">21 </span><span class="subxS1Comment"># . size = 1 character</span>
<span id="L22" class="LineNr">22 </span>ba/copy-to-edx 1/imm32
<span id="L23" class="LineNr">23 </span><span class="subxS1Comment"># . syscall</span>
<span id="L24" class="LineNr">24 </span>e8/call <a href='../000init.subx.html#L23'>syscall_read</a>/disp32
<span id="L25" class="LineNr">25 </span>
<span id="L26" class="LineNr">26 </span><span class="subxComment"># write(stdout, X, 1)</span>
<span id="L27" class="LineNr">27 </span><span class="subxS1Comment"># . fd = 1 (stdout)</span>
<span id="L28" class="LineNr">28 </span>bb/copy-to-ebx 1/imm32
<span id="L29" class="LineNr">29 </span><span class="subxS1Comment"># . initialize X (location to read from)</span>
<span id="L30" class="LineNr">30 </span>b9/copy-to-ecx <span class="SpecialChar"><a href='ex4.subx.html#L10'>X</a></span>/imm32
<span id="L31" class="LineNr">31 </span><span class="subxS1Comment"># . size = 1 character</span>
<span id="L32" class="LineNr">32 </span>ba/copy-to-edx 1/imm32
<span id="L33" class="LineNr">33 </span><span class="subxS1Comment"># . syscall</span>
<span id="L34" class="LineNr">34 </span>e8/call <a href='../000init.subx.html#L29'>syscall_write</a>/disp32
<span id="L35" class="LineNr">35 </span>
<span id="L36" class="LineNr">36 </span><span class="subxComment"># exit(ebx)</span>
<span id="L37" class="LineNr">37 </span>e8/call <a href='../000init.subx.html#L18'>syscall_exit</a>/disp32
<span id="L38" class="LineNr">38 </span>
<span id="L39" class="LineNr">39 </span><span class="subxS2Comment"># . . vim:nowrap:textwidth=0</span>
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