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# Strings

A string can be mutable or immutable. When an immutable string is provided to a procedure like `string-set!`, the `exn:application:type` exception is raised.

String constants generated by `read` are immutable. `(string->immutable-string string)` returns an immutable string with the same content as string, returning string if it is already an immutable string.

When a string is created with `make-string` without a fill value, it is initialized with the null character (`#\nul`) in all positions.

The string comparison procedures -- `string=?`, `string-ci=?`, etc. -- take one or more string arguments and check the arguments pairwise (like the numerical comparison procedures).