Return function of different return values

return 0; commonly 0 It represents the normal end

return -1; -1 Represents an abnormal end

return ; void The return is empty ,void The return value can write nothing , Can write return;

return NULL; If the data type is a pointer type , Then we usually return the corresponding address when we succeed , Return when you fail NULL

About NULL, I'll simply write it down as Use... When describing the address NULL‘ Zero clearing ’, When describing data use 0 Zero clearing .