Boolean Logic and Logic Gates

The three basic gates

Gate	Symbol notation	Output is 1 when…
AND	A · B	both inputs are 1
OR	A + B	either input is 1
NOT	¬A	the input is 0 (it inverts)

Truth tables

A B | AND  OR
0 0 |  0    0
0 1 |  0    1
1 0 |  0    1
1 1 |  1    1

A | NOT A
0 |   1
1 |   0

Combining gates

Q = A AND (NOT B) — build the table column by column:

A B | NOT B | A AND NOT B
0 0 |   1   |     0
0 1 |   0   |     0
1 0 |   1   |     1
1 1 |   0   |     0

Exam tip

Build truth tables one column at a time, working from the innermost brackets outwards. AND needs both 1; OR needs at least one 1; NOT flips the value.