Boolean logic · Digital circuits

Logic Gates

Wire AND / OR / NOT / XOR. The primitives every CPU is built from.

Every CPU on Earth is built from a small set of logical primitives: AND, OR, NOT, XOR. Compose them and you can implement any computation. The patterns you wire here are the same patterns inside an addition circuit, a memory cell, and every Boolean condition you'll ever write in code.

AND Gate &

→

A	B	Out
0	0	0
0	1	0
1	0	0
1	1	1

Output is 1 only when both inputs are 1

OR Gate |

→

A	B	Out
0	0	0
0	1	1
1	0	1
1	1	1

Output is 1 when either input is 1

NOT Gate !

→

A	Out
0	1
1	0

Output is the opposite of the input

Challenge

Make the light turn green! The rule is: A AND (NOT B).
Turn on A and turn off B.

→NOT B →AND →

What you just learned

Every computer is made of billions of tiny logic gates — switches that decide yes or no based on simple rules. AND, OR, and NOT are the building blocks of everything a computer does.

What’s happening under the hood

›Boolean algebra: 0 and 1, AND/OR/NOT operations. George Boole (1854) → Claude Shannon (1937, applied to switching circuits) → every digital computer that followed.
›Functional completeness: NAND alone can express every logical operation. Real CPUs are built from billions of these primitives etched into silicon.
›Boolean expressions in your code (`if (x > 0 && !done)`) compile down to these same gate operations on the CPU's ALU.

Dig deeper

Phase 0 · How Computers Think

The concept you just explored is taught with full depth in the formal DURA curriculum.