2.1 The rules

Binary subtraction has simple rules, just as binary addition as discussed in module 0217.

• 0 - 0 = 0 with a borrow of 0.
• 1 - 0 = 1 with a borrow of 0.
• 0 - 1 = 1 with a borrow of 1.
• 1 - 1 = 0 with a borrow of 0.