When the mobile phone memory card sends a short message, the system prompts that the storage space is full. What happened?

This means that the phone memory is full. The mobile phone will leave a certain amount of memory on the internal memory of the mobile phone, such as phone book, short message, etc. To store contacts and text messages! However, the space left is limited. When the memory occupied by SMS or the contacts stored in the mobile phone reach the warning line of allocated space, a prompt of "storage space is full" will appear. Of course, contacts generally don't take up much space, so you rarely see this hint when storing contacts! I hope you have deleted the old useless messages!