CustomChar sets one of the 8 CGRAM locations with a custom character. The custom character can be used by writing a byte of value 0 to 7. When you are using LCD as 5x8 dots in function set then you can define a total of 8 user defined patterns (1 Byte for each row and 8 rows for each pattern). Use http://www.8051projects.net/lcd-interfacing/lcd-custom-character.php to create your own characters. To use a custom character, write byte value of the custom character position as a string after having setup the custom character.