Binary-Coded Decimal (BCD)

Why it matters

BCD keeps decimal math exact for money and calculators. Understanding shapes storage and arithmetic.

The architecture

Packed BCD: two digits per byte.

Add-3 correction for overflow.

Slower than binary but decimal-exact.

How it works end to end

Calculators use BCD.

IBM mainframes offer BCD arithmetic.

Databases may use decimal types for money.