Lab0 / Learn, build, explore

Logic playground

Build circuits from gates. Learn a 4-bit calculator, then make it your own.

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01 / Tiny switches

Meet the bits

A bit is a switch: off is 0, on is 1. Four switches have place values 8, 4, 2, 1, so they represent numbers from 0 to 15. The rightmost switch is bit 0. Use the A and B controls in the circuit editor. The result is computed by the gates and wires you can edit.

Your mini mission

Make A = 9: turn on the 8 and 1 switches. Make B = 3: turn on 2 and 1.

Operand A

Operand B

4-bit result 1000 = 8Carry-out: 0Inspect

The display is driven by your circuit’s wires. Change a gate or disconnect a wire to see how the result changes. SUB flips B and supplies the first carry.

Drag parts onto the canvas. Connect pins to wire.

OutputsS0 0S1 0S2 0S3 1Cout 0

Truth table

The truth table is too big for more than 4 inputs.

Pocket checkpoint

Which four bits represent decimal 9?

100101101111