I have a question, I downloaded the program into Raspberry Pi pico when I was working on the project of thermal printer parking system, after that I tried to copy other programs but they failed, is it because the pico board can only copy one program?
Nah you can have ‘multiple things’ running on the pico at once.
In this instance the processor was busy when you tried writing the program so it couldnt read the USB input at the same time, interupting the processor with ‘ctrl + C’ breaks out of the program and back into the REPL so you can reflash the Pico.
More about using both Cores on the Pico: #372 How to use the two Cores of the Pi Pico? And how fast are Interrupts? - YouTube
Plus the PIO can be used completely independent of the processor!