A storage device comprises a plurality of bitwise-modifiable memory cells. A control device is also provided, which, in order to modify existing data content written to a group of memory cells with new data content to be written, is designed to compare the existing data content and the data content to be written in order to obtain a comparison result. The control device is designed to determine a subset of the group of memory cells for modification and a remaining length based on the comparison result, and to write the data content to be written to the subset, leaving the remaining set at least partially unchanged. For modifying the existing data content, the storage device is designed to read from a memory location of the storage device and to verify the correctness of the memory location.