A method of operating a memory array is disclosed. The memory array includes a plurality of memory cells arranged in rows and columns, wherein a plurality of parallel memory strings correspond to respective ones of the columns, and a plurality of word lines are arranged orthogonal to the plurality of memory strings, each word line being connected to gate electrodes of a corresponding one of the rows of memory cells. The method includes performing a program operation that programs all of the memory cells on edge word lines located at opposite edges of the memory array, and that programs selected memory cells between the edge word lines in the memory array according to input data to be stored in the memory array. Each programmed memory cell has a threshold voltage at a program verify (PV) level.