Blood Type Compatibility Can Be Modeled With Simple Bitwise Operations

A technical analysis published on DEV Community demonstrates that blood transfusion compatibility rules can be represented using 3-bit binary masks instead of complex conditional logic. Each of the eight primary blood types is assigned a unique integer from 0 to 7, with individual bits representing the presence or absence of A, B, and Rh antigens. A single bitwise operation — checking whether the donor's antigen mask contains any bits not present in the recipient's mask — determines compatibility in constant time. This approach mirrors the underlying biochemistry, where a recipient's immune system rejects any antigen it does not already carry. The compatibility relationships also form a directed graph, with O- as the universal donor at the base and AB+ as the universal recipient at the top.