From GridLAB-D Wiki
Character strings of 256 characters or less are stored in a char256 built-in data type.
An attempt to store a string longer than the maximum number of characters permitted results in truncation of the string to a length that fits.
GLM
To declare a char256 value in a class use the syntax
class my_class {
char256 my_string;
}
To define a string value in an object use the syntax
object my_class {
my_string "value";
}
where "value" is a string of 256 or fewer characters..