Memory device and a memory system including the same

An operating method of a memory device comprising a plurality of memory cells forming a plurality of strings in a vertical direction with a substrate, the operating method comprising:

• detecting a not-open string (N/O string) from the plurality of strings in response to a write command;
• converting, to have a value, pieces of target data to be programmed on a plurality of target memory cells in the N/O string;
• and
• performing a program operation on the plurality of memory cells.

A memory system, comprising:

• a memory device comprising a plurality of blocks each block comprising a plurality of memory cells arranged in a vertical direction with respect to a substrate;
• and
• a memory controller configured to control a memory operation of the memory device,
• wherein the memory device is configured to perform, while programming a target block in response to a write command received from the memory controller, a conversion operation on pieces of target data that are to be programmed on a plurality of target memory cells in at least one not-open string (N/O string) of the target block, such that the pieces of target data have a value that limits a number of times a program voltage is applied to the plurality of target memory cells.