1. A method of operating a memory system comprising a multi-bit memory device, comprising: determining whether a requested program operation is a random program operation; where the requested program operation is determined to be a random program operation, determining whether a selected memory block of a current program operation is an open block, and upon determining that the selected memory block is an open block, performing a fine program operation on coarse-programmed memory cells in the selected memory block before performing the random program operation; determining whether the requested program operation is an open block program operation; and where the requested program operation is determined to be an open block program operation, storing program data of the open block program operation in the selected memory block.