Half Adder

Splashery stretches a drumhead over this Splash's outline, twelve inches across, and finds the ways it can ring. Its lowest is 324.4 Hz, 72 cents sharp of E♭4, the nearest tine on the comb. The next fifteen are its overtones, and each one draws its own figure: sand gathers on the lines that stay still.

Tap it to add 1 + 1. Hands-on: flip each lever by hand; the lamps show the sum.

A half adder adds two bits, each 0 or 1. Its XOR gate gives the sum bit: 1 when exactly one input is 1. Its AND gate gives the carry: 1 when both inputs are 1. With carry written first, 0 + 0 gives 00, 0 + 1 and 1 + 0 give 01, and 1 + 1 gives 10.

Tap to watch the fixed 1 + 1 example. Both switches flip to 1, light travels through the gates, and only the carry lamp lights: binary 10 means two. Then the switches reset. There is no incoming carry on a half adder. Two half adders plus an OR gate can make a full adder, which also accepts that carry; chaining full adders adds longer binary numbers. With ✋ Hands-on on, flip each lever by hand: the lamps show the sum and the carry of the two bits at once, so 0 + 1 = 1 and 1 + 1 = 10.

The gate explanation and fixed 1 + 1 example are correct. The animation lights the carry and leaves the sum dark, giving binary 10. It does not let the reader choose all four input pairs.

1. Correct

   XOR produces the sum and AND produces the carry.¹

   The About truth table gives 00, 01, 01, 10 for 0+0, 0+1, 1+0, 1+1; the actual fixed animation ends at carry 1 and sum 0.

2. Correct

   The animated answer for 1 + 1 is binary 10.¹

   Both input lamps become one, only the carry output lights, and the sequence then resets. This also runs in the browser.

3. Correct

   A half adder has no incoming carry; a full adder can combine two half adders and an OR gate.¹

   The About text distinguishes the two circuits; no full adder is presented as part of this splash.

4. Simplified

   The circuit picture repeats a fixed worked example.¹

   The driver selects display stages; there is no input-dependent Boolean evaluator for all four cases.

1. 1Half adder, All About Circuits textbook

Simplified

Only the fixed 1 + 1 sequence is animated. The other truth-table rows are explained in the About text, not computed by interactive inputs.

Made in Splashery. Its code is MIT.

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