mode can be specified in either absolute or symbolic form. An absolute mode is an octal number constructed from the OR of the following modes:
04 read 02 write 01 executeSymbolic mode is any combination of the letters r (read) w (write), and x (execute). It is an error to try to read any file that does not read permission set, to try to write any file that does not have write permission set, or to try to execute any file that does not have execute permission set.
size specifies how many 52 byte blocks to allocate for the file and should be set large enough for your application. The file name can be up to 12 characters long.