the nth element (zero-based) of a string
Major Section:  PROGRAMMING

(Char s n) is the nth element of s, zero-based. If n is greater than or equal to the length of s, then char returns nil.

(Char s n) has a guard that n is a non-negative integer and s is a stringp.

Char is a Common Lisp function. See any Common Lisp documentation for more information.