RScheme has a wide variety of string manipulation functions, providing facilities that are useful to normal programmers and going well beyond what's available in [R4RS].
Consider for example the following string:
Note the numbering assigned to the characters in the string. For purposes of array operations like string-ref, since arrays are 0-based in Scheme, the referenced character is the character that would make up a substring with an offset equal to the given index, and having length 1.