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The Logic

  1. 01The Logic
  2. 02The connection
  3. 03Try it yourself
  4. 04What did you notice?
  5. 05Both must agree
  6. 06Either will do
  7. 07Here's an analogy to hammer home the point
  8. 08The inverter
  9. 09Gates talk to each other
  10. 10Three gates, one circuit
  11. 11Three rules
  12. 12Building logic
  13. 13A simple comparison
  14. 14Turn the rule into gates
  15. 15Flip before you compare
  16. 16Small rules stack up
  17. 17Take a breath
  18. 18What is 1+1?
  19. 19Addition, from scratch
  20. 20Two gates, that's it
  21. 21Memory
  22. 22Reinforce your understanding
  23. 23Question: AND gate
  24. 24Question: NOT gate
  25. 25Question: Binary addition
  26. 26Quiz: answer
  27. 27One switch
  28. 28Want to go deeper?
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Memory

There is one last piece of the puzzle that we have not talked about yet. Memory. How does a computer remember things?

Every gate we've looked at forgets the moment its input changes. It only knows right now.

But take a gate's output and feed it back into its own input and something changes. The circuit holds its state. The state stays locked in place. It remembers the last thing that happened, even after the input is gone.

That loop is called a latch. It's the simplest memory a computer has.

Did you know?

The Apollo missions needed software to fly the spacecraft to the Moon. That software was written on other computers first. But to load it into the spacecraft, workers had to weave it by hand: a wire threaded through a tiny ring meant 1, around it meant 0. The code became woven wire.

Gates that decide. Gates that remember. That's the whole foundation.

Citations(3)↓
  1. 1. allaboutcircuits.com
  2. 2. nand2tetris.org
  3. 3. spectrum.ieee.org
Citations(3)↓
  1. 1. allaboutcircuits.com
  2. 2. nand2tetris.org
  3. 3. spectrum.ieee.org