Sheffer

Sheffer is a surname that appears in various scientific and scholarly contexts. In logic, the term most commonly refers to the Sheffer stroke, also known as the NAND operator. The Sheffer stroke is a binary connective denoted by p | q and is true exactly when at least one of p or q is false; equivalently, p | q equals not (p and q). The operator is functionally complete, meaning that any Boolean function can be expressed using only NAND operations.

Because of its universality, the Sheffer stroke is widely used in digital circuit design and theoretical computer science. Examples of expressions using only NAND include: not p equals p | p; p and q equals (p | q) | (p | q); and p or q equals (p | p) | (q | q). The stroke’s simplicity and ability to simulate all basic logic gates have made it a fundamental tool in teaching, research, and hardware implementation.

The name “Sheffer stroke” honors Henry M. Sheffer, who introduced the operator in the early 20th century. Beyond this central topic, the surname Sheffer may refer to various individuals who have contributed to mathematics, science, and academia, though specific attributions are context-dependent.

In summary, Sheffer most often points to the NAND-based Sheffer stroke in logic, a single operator capable of expressing all Boolean operations, and it is named after its proponent, Henry M. Sheffer. The term can also denote people who bear the surname in different fields.