LED display screen upper computer and lower computer communicate.

For communication, using the rs232 level conversion chip, you can use the computer and 89c51 for serial communication.

If you want to retain data when the power is turned off, your circuit must use a data retention memory. You can use a flash chip (more expensive) or a serial EEprom chip, which is relatively cheap. These can retain data even when the power is turned off.

You can also use Ram+ memory battery (data will be lost if the battery is powered off).

As for programs, write programs for serial communication and data saving and reading.

I won’t mention the dot matrix display program.

If your design has a font library, the data transmitted by your host computer will be one Chinese character per double byte.