String data is left justified (i.e., no leading blank space) with trailing blanks optional, which may be trimmed, and SHOULD be ignored on string compare operations for 2 values of type ST. Any displayable (printable) characters are allowed based on the character set identified in MSH-18. For the default ASCII character set this is hexadecimal values between 20 and 7E, inclusive, or decimal values between 32 and 126, except the defined escape characters and defined delimiter characters. For Unicode this is any code point with a Basic Type of Graphic, except the defined escape characters and defined delimiter characters; see The Unicode Standard section 2.4 <http://www.unicode.org/versions/Unicode10.0.0/ch02.pdf> for details.
Primitive Type
This is a primitive data type with no internal structure. It represents a single value.