When LispWorks for Windows starts up on a OS with a non-Latin-1 code page, it calls
so that by default, newly constructed strings can contain the data likely to be returned from the OS or user input.
If you know your string only needs to contain 8-bit data, then you can create it explicitly with element type
Conversely if you know that a string may need to contain 16-bit data even on a Latin-1 code page system, then you should create it explicitly with element-type simple-char.
LispWorks User Guide and Reference Manual - 21 Dec 2011