Memory system with semiconductor storage device and memory controller for performing read verification

A memory system comprising:

• a memory controller;
• and
• a semiconductor storage device including a plurality of memory cells,
• wherein, if data is written to the plurality of memory cells, the memory controller transmits a write command to the semiconductor storage device,
• with respect to the write command,
• the semiconductor storage device is configured to:
• perform a program operation including performing a first software program loop until a first predetermined condition is satisfied, wherein the first software program loop includes applying a write voltage to a word line, applying a first verification voltage to the word line to perform program verification for performing write determination of a first data value provided in the data, and increasing a set value of the write voltage if determining that writing of the first data value is not completed;
• generate an index based on first information obtained according to a progress of writing the first data value in the program operation, and
• the memory controller is configured to send a first command for acquiring the index,
• the semiconductor storage device is configured to send the index in response to the first command, and
• the memory controller is configured to receive the index sent from the semiconductor storage device and determine whether to perform read verification of reading data from the plurality of memory cells based on the received index.