Library: Base
Introduced: 2.0 Beta 1


The buffer simply passes through to its right output whatever input it receives on the left side. The truth table for a one-bit buffer is the following.


If the input is unspecified (i.e., floating), then the output will also be unspecified - unless the "Gate Output When Undefined" option is "Error for undefined inputs," in which case the output is an error. If the input is an error value, then the output will also be.

Buffers are the most useless of the gate components provided in Logisim; its presence in the Gates library is just as much a matter of completeness (a component for each possible one-input truth table) as it is a matter of providing useful functionality. Still, it can be occasionally useful to ensure that values propagate in only one direction along a wire.

Pins (assuming component faces east)

West edge (input, bit width according to Data Bits attribute)
The input into the component.
East edge (output, bit width according to Data Bits attribute)
The output, which always matches the input into the left side.


When the component is selected or being added, Alt-0 through Alt-9 alter its Data Bits attribute and the arrow keys alter its Facing attribute.

The direction of the component (its output relative to its input).
Data Bits
The bit width of the component's inputs and outputs.
The text within the label associated with the gate.
Label Font
The font with which to render the label.

Poke Tool Behavior


Text Tool Behavior

Allows the label associated with the gate to be edited.

Back to Library Reference