MEMORY SYSTEM AND METHOD OF OPERATING THE SAME

A memory system includes a flash memory device including a first memory block group on which a least significant bit (LSB) program operation has been performed and a program operation on another bit has not been performed and a second memory block group on which both the LSB program operation and a most significant bit (MSB) program operation have been performed and a memory controller configured to check which of the first and second memory block groups a memory block selected for an LSB data read operation belongs to and set a level of a read voltage for the LSB data read operation of the selected memory block.