Nonvolatile memory device, methods of programing the nonvolatile memory device and memory system including the nonvolatile memory device

A method of programming a nonvolatile memory device including a memory cell array including memory cells configured to store first-bit data and second-bit data, the method comprising:

• receiving second-bit data to be programmed into memory cells of a first word line among a plurality of word lines of the memory cell array;
• backing up first-bit data stored in memory cells of a second word line adjacent to the first word line;
• and
• subsequent to the backing up, programming the received second-bit data in the memory cells of the first word line.

A method of programming a nonvolatile memory device including memory cells, each cell configured to store at least first-bit data and second-bit data, the method including:

• receiving first data including first-bit data to be programmed to memory cells connected to a particular word line of the nonvolatile memory device;
• receiving second data including first-bit data to be programmed to memory cells connected to a different word line of the nonvolatile memory device;
• receiving third data including second-bit data to be programmed to the memory cells connected to the particular word line of the nonvolatile memory device;
• programming the first data to the memory cells connected to the particular word line and programming the second data to the memory cells connected to the different word line, prior to programming the third data to the particular word line;
• and
• storing backup data including a copy of the second data in a backup circuit, prior to programming the third data to the particular word line.