Binary Subtraction

Subtracting binary numbers uses the same borrowing concept as decimal. When you subtract a larger digit from a smaller one, borrow from the next column.

Rules: $0 - 0 = 0$, $1 - 0 = 1$, $1 - 1 = 0$, $0 - 1$ requires borrowing (borrow 1 from next column, making it $10 - 1 = 1$). Example: $1010 - 0011$. Work right to left with borrowing as needed. Result: $0111$.

Computers rarely use subtraction directly. Instead, they add negative numbers using two's complement. This unifies addition and subtraction into one circuit, saving hardware. Let me show you how that works.