We'd like to use analytics cookies to understand which symbols people look up, so we know what to research next. They are not used for advertising and we set none of them unless you say yes. What we store.
Small candidate numbers written in a cell's corners or centre.
Also known as: Candidate marks, Corner marks, Sudoku notation
Pencil marks are the small numbers a solver writes inside an empty sudoku cell to record which digits could still go there. Two conventions coexist and mean different things: corner marks list every candidate for that cell, while centre marks are used in some solving styles to note a restricted set. The distinction matters because a technique that scans for a digit appearing exactly twice in a unit is only visible if the marks are complete.
Uses two conventions that are not interchangeable: corner marks list every remaining candidate for the cell, while centre marks note a restricted set within a solving style. Techniques that scan for a digit appearing exactly twice in a unit only work if the marks are complete.
Contexts: Software
Several very small numerals arranged in the corners or the middle of an otherwise empty square cell within a ruled grid.
Both are notations solvers add to a printed puzzle.