The Karnaugh map is a useful graphical tool for minimizing switching functions of up to six variables. A four-variable map has 16 fields, each corresponding to a unique conjunction (AND) of inputs (a minterm). Click a field of the map to add or remove a minterm. The disjunction (OR) of the minterms defines the switching function. The expression for the minimized disjunctive normal form (or sum of products form) for the switching function is given below the map.