A nonvolatile memory device includes a nonvolatile memory cell array, where N bits are stored in a single memory cell (N being an integer greater than or equal to 2), and a page buffer circuit electrically connected to the nonvolatile memory cell array. The page buffer circuit includes at least N latches configured to temporarily store data. A data input/output circuit connected to the page buffer circuit receives programmed input data and provides the input data to the page buffer circuit. A control logic controls the page buffer and initializes a target latch value before receiving all input data of a program unit from the data input/output circuit.