Disclosed is a nonvolatile memory system including at least one nonvolatile memory each having a plurality of nonvolatile memory cells and a buffer memory; and a control device coupled to the nonvolatile memory. The control device is enabled to receive external data and to apply the data to the nonvolatile memory, and the nonvolatile memory is enabled to operate a program operation including storing the received data to the buffer memory and storing the data held in the buffer memory to ones of nonvolatile memory cells. Moreover, the control device is enabled to receive external data while the nonvolatile memory is operating in the program operation. Also, the buffer memory is capable of receiving a unit of data, equal to the data length of data to be stored at one time of the program operation, the data length being more than 1 byte.