Semiconductor memory device, memory system including the same and operating method thereof

A semiconductor memory device, comprising:na program and read unit temporarily storing program data including a first bit data and a second bit data, programming the program data temporarily stored in a memory cell array, or reading data stored in the memory cell array; anda control unit suitable for generating a control signal for controlling the program and read unit in response to a command input from the outside of the semiconductor memory device,wherein the control unit controls the program and read unit to stop programming the program data when a read command is input while programming the program data, and perform a read operation while maintaining the first bit data stored when programming the program data.

A method of operating a semiconductor memory device, comprising:nstoring a program data including a first bit data and a second bit data in a program and read unit, and subsequently, performing a program operation according to the program data stored in the program and read unit;inputting a read command during the program operation;performing a read operation by the program and read unit in response to the read command, wherein the first bit data stored in the program and read unit during the program operation remains in the program and read unit during the read operation; andre-inputting the second bit data from an external device and resuming the program operation from a point of time when the program operation is stopped when the read operation is completed.