A string is a sequence of characters between double quotes. LISP represents a string as a variable-length array of characters. You can write a string which contains a double quote by preceding the quote with a backslash; a double backslash stands for a single backslash. For example:
"abcd" has 4 characters
"\"" has 1 character
"\\" has 1 character
Here are some functions for dealing with strings:
> (concatenate 'string "abcd" "efg")
"abcdefg"
> (char "abc" 1)
#\b ;LISP writes characters preceded by #\
> (aref "abc" 1)
#\b ;remember, strings are really arrays
The concatenate function can actually work with any type of sequence:
> (concatenate 'string '(#\a #\b) '(#\c))
"abc"
> (concatenate 'list "abc" "de")
(#\a #\b #\c #\d #\e)
> (concatenate 'vector '#(3 3 3) '#(3 3 3))
#(3 3 3 3 3 3)