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- <title>Tool Attributes</title>
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- <h1>Tool attributes</h1>
- <p>Every tool for adding components to a circuit also has a set of
- attributes, which are imparted to the components created by the tool,
- although the components' attributes may be changed later without
- affecting the tool's attributes. When you select a tool, Logisim
- will change the attribute table to display that tool's attributes.</p>
- <p>For example, suppose we want to create smaller AND gates.
- Right now, each time we select the AND tool, it creates a large AND gate.
- But if we edit the Gate Size attribute just after selecting the tool (before
- placing its AND gate into the circuit), we'll be changing
- the attributes for the tool, so that future AND gates added using the tool
- would be narrow instead.</p>
- <center><img src="../../../img-guide/attrlib-and-narrow.png" width="505" height="301"></center>
- <p>Now, we can delete the two existing AND gates and add two new
- AND gates in their place. This time, they will be narrow.
- (If you chose to reduce the number of inputs to 3, the AND gate
- would not have vertical extension on the left side. But you'd also
- have to rewire the circuit so that the wires hit the AND gate's left
- side.)</p>
- <center><img src="../../../img-guide/attrlib-and-replace.png" width="505" height="299"></center>
- <p>With some tools, the tool's icon reflects some of the attributes'
- values. One example of this is the Pin tool, whose icon
- faces the same way as its Facing attribute says.</p>
- <p>The tools in the toolbar each have a separate attribute set from
- the corresponding tools in the explorer pane. Thus, even though we
- changed the toolbar's AND tool to create narrow AND gates, the AND
- tool in the Gates library will still create wide AND gates unless
- you change its attributes too.</p>
- <p>In fact, the input pin and output pin tools in the default
- toolbar are both instances of the Wiring library's Pin tool, but
- the attribute sets are different. The icon for the Pin tool
- is drawn as a circle or a square depending on the value of its
- "Output?" attribute.</p>
- <p>Logisim provides a handy shortcut for changing the Facing attribute
- that controls the direction in which many components face: Typing an
- arrow key while that tool is selected automatically changes the
- direction of the component.</p>
- <p><strong>Next:</strong> <em><a href="../index.html">User's Guide</a>.</em></p>
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