One-Pager — Digital Electronics (P1 Rank 2)

• Binary weights: … 16 8 4 2 1
• Hex digits 0–9 A–F; 1 hex = 4 bits; 1 octal = 3 bits
• 1's complement = invert; 2's = invert + 1 (used for signed)
• Gates: AND (all 1), OR (any 1), XOR (odd 1s), NAND/NOR universal
• De Morgan: break bar, change +↔·
• Half adder: Sum=A⊕B, Carry=AB; Full adder needs Cin
• SR, JK, D, T flip-flops store 1 bit; JK no invalid when J=K=1 (toggles)
• MUX: many→1; DEMUX: 1→many; Encoder: 2ⁿ→n; Decoder: n→2ⁿ

Practice: practice/topic-mcqs/02-digital-electronics.md