Character string constants, and bit constants longer than 32 bits, are stored as string constants.
A string constant is represented by a descriptor, a fixed value containing
the length of the string in the high-order byte and the address of the string in the low-order
The maximum length of a string constant is 256 characters, or 2048 bits. The null string
represented by '' is a string of zero length. Two successive single quotes within a
character string constant are used to represent one single quote.
The following are valid character strings:
'I don''t think so.'