Part 1 · Basics · levels 1–16

The main ideas of the part

• A signal is 0 or 1. A wire computes nothing — it just carries a bit from a source to a receiver.
• Every gate can be built from NAND: NOT, AND, OR and XOR appear one by one as combinations of what you already have.
• Devices grow out of gates: an adder adds, a multiplexer chooses, an SR latch remembers.
• Eight bits are a byte: the bus, the register and the ALU work on eight wires at once, not on one.
• A clock turns a circuit into an automaton: the program counter walks through addresses, one per tick.

What you will have built by the end

By the end of the part you will have built an 8-bit adder, an eight-operation ALU, a register out of D flip-flops and a program counter — the complete teaching datapath assembled at level 16.

Levels of the part

1. 1. Let there be light! — explain what a 0/1 signal, an input/output pin, and a wire are, and connect a source to a receiver Open in the game →
2. 2. Negation — derive a NOT from a tied-input NAND and explain NAND's universality Open in the game →
3. 3. Perfect pair — build an AND from NAND + NOT and explain operation composition Open in the game →
4. 4. At least one — build an OR using De Morgan's law and explain the formula NOT(NOT A AND NOT B) Open in the game →
5. 5. Strict choice — build an XOR from basic gates and explain it as a "controlled inverter" Open in the game →
6. 6. Half Adder — explain how adding two bits yields two outputs (Sum, Carry) and build a half adder Open in the game →
7. 7. Full Adder — explain carry propagation between bits and build a full adder Open in the game →
8. 8. 8-bit Adder — explain what a bus and a byte are, and build an 8-bit adder as a chain of carries Open in the game →
9. 9. Crossroads — build a multiplexer, verify its selection formula, and explain it as a "digital switch" Open in the game →
10. 10. Loopback — build an SR latch from two NOR gates, verify state retention, and explain the role of feedback Open in the game →
11. 11. Smart memory — build a master-slave D flip-flop and demonstrate on clock ticks why state changes only on the edge Open in the game →
12. 12. Tangible Memory — break the register by disconnecting Clock from the flip-flops, and explain how 8 flip-flops form a byte-wide register Open in the game →
13. 13. Operation Selection — build a multiplexer cascade and show how OpSelect routes the result of the required operation Open in the game →
14. 14. Heart of math — break the ALU in a specified way (result around the MUX) and explain the decoder → operations → MUX architecture and the Zero flag Open in the game →
15. 15. System Pulse — explain how a clock moves data through registers and manually clock a counter Open in the game →
16. 16. Program Counter — build a program counter and explain the register → ALU → register cycle Open in the game →

Each level number leads to its library guide; "Open in the game" goes straight to the level in the simulator.