Small gates.
Big possibilities.
Inputs are the signals that go into a gate. The output is the result.
Change an input, work out the result, then build your own circuit.
Name: ______________________________ Date: ________________
Meet the building blocks.
Choose a gate. Try its inputs. Then fill in the truth table to show what happens in every case.
AND gate
Select an input button to change it from 0 to 1, or from 1 to 0.
Your truth table
2 inputs · 4 rowsY is the output. Choose 0 or 1 for each row. The highlighted row shows the inputs you are testing now.
0 and 1 are logic states
0 means LOW. 1 means HIGH. Real gates use low and high voltage ranges. Those ranges depend on the type of chip and its power supply.
An overbar means NOT
NOT A means “NOT A”: change 0 to 1, or 1 to 0. This is called inversion. A small circle on a gate symbol means the same thing.
Count every combination
Two inputs need 4 rows. Three need 8. Each extra input doubles the rows. The rule is 2n, where n is the number of inputs.
Make the connections.
Choose where each gate gets its inputs. Follow the connections to work out Y.
Circuit controls
G1 means Gate 1, G2 means Gate 2, and so on. For each input, choose a source: A–D or the output of an earlier gate.
Loading an example clears your current circuit and table answers.
Scroll across larger circuits. Crossing wires connect only at a marked dot.
Read the connections as text
Reveal the Boolean expression
A Boolean expression is a short way to write what a logic circuit does. This one shows every gate step. An overbar means NOT for everything under the bar.
Circuit truth table
Fill in G1 first, then G2, and keep going. Use those results to find Y. Changing a connection clears your table answers.
Put your logic to work.
Read the goal, then build a circuit that does the job. There may be more than one correct design.
Lab guide & accessibility
Read the symbols
- A · B means A AND B.
- A + B means A OR B. Here, + is a logic symbol; it does not mean add the numbers.
- A ⊕ B means A XOR B: exactly one input is HIGH.
- An overbar means NOT. First solve everything under the bar. Then change its result from 0 to 1, or from 1 to 0.
- NAND gives the opposite result of AND. NOR gives the opposite result of OR. XNOR gives the opposite result of XOR.
This lab shows the final 0 or 1 after the inputs change. It does not show the small delays inside real gates, unconnected inputs, or limits on how many parts a gate can drive.
Use the lab your way
- Use Tab to move forward and Shift+Tab to move back. Press Enter or Space to use a button. Use the arrow keys to choose from a menu.
- Use the labeled menus to make every connection. You do not need to drag wires.
- Each signal shows a 0 or 1. Screen readers can read the expressions in words. You can also read a text list of the connections.
- Take as much time as you need. You can zoom in or use a small screen. Print worksheet gives you a blank table for the activity you are viewing.
- Your work stays in this page. Reloading the file starts the lab over. Save an answer key before closing if you want to keep the correct table values. The CSV file opens in a spreadsheet app.
Designed toward WCAG 2.2 AA. Software checks alone cannot confirm that every accessibility need is met. Testing with screen readers and other access tools is still needed.