Memory device and memory system

A memory device, comprising a memory string configured to store first stored data, and configured to compare the first stored data and first input data to generate a first current signal, the memory string comprising a plurality of switch elements coupled in series with each other, the plurality of switch elements comprising:

• a first switch element configured to receive a first word line signal, have a first threshold voltage when the first stored data has a first value, and have a second threshold voltage when the first stored data has a first encoding range;
• and
• a second switch element configured to receive a second word line signal, have the second threshold voltage when the first stored data has the first value, and have the second threshold voltage when the first stored data has the first encoding range,
• wherein the first encoding range at least comprises the first value and a second value different from the first value.