RULE 1 — Position = Power
Rightmost bit = 2⁰ = 1. Each step left doubles the value.
RULE 2 — Only 1s Add Value
A bit of 0 contributes nothing. Only 1s get multiplied by their place value.
RULE 3 — Sum It All
Add all the place values where a 1 appears. That's your decimal.
RULE 4 — Max 8-bit = 255
11111111 = 128+64+32+16+8+4+2+1 = 255. That's why one byte holds 0–255.