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	<title>Generating a circuit</title>
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<h1>Generating a circuit</h1>

<p>The Build Circuit button will construct a circuit whose gates
correspond to the currently chosen expressions for each output. The
circuit's inputs and outputs will be displayed in top-down order
corresponding to how they appear under the Inputs and Outputs
tabs. Generally speaking, the constructed circuit will be attractive;
and, indeed, one application of Logisim's Combinational Analysis
module is to beautify poorly drawn circuits. Still, as with any
automatic formatting, it will not express the structural details that
a human-drawn circuit would.</p>

<center><img src="../../../../en/img-guide/analyze-circuit.png" width="315" height="398"></center>

<p>When you click the Build Circuit button, a dialog box will appear
prompting you to choose which project where you want the circuit and
the name you wish to give it.</p>

<center><img src="../../../../en/img-guide/analyze-build.png" width="321" height="168"></center>

<p>If you type the name of an existing
circuit, then that circuit will be replaced (after Logisim prompts
you to confirm that you really want to do this).</p>

<p>The Build Circuit dialog includes two options. The Use Two-Input
Gates Only option specifies that you want all gates constructed to have
two inputs.  (NOT gates, of course, constitute an exception to this
rule.)  The Use NAND Gates Only option specifies that you would like
it to translate the circuit into one using only NAND gates. You can
select both options if you want to use only two-input NAND gates.</p>

<p>Logisim cannot construct a NAND-only circuit for an expression
containing any XOR operators. This option will therefore be disabled
if any outputs' expressions contain XORs.</p>

<p><strong>Next:</strong> <em><a href="../index.html">User's Guide</a></em>.</p>

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