just like the standard sprintf() function in C, but
the format is a counted string and accepts %#s to
be the format-symbol for a forth-counted string.
The result is a zeroterminated string at dest$ having
a length being returned. To create a forth-counted
string, you could use:
variable A 256 ALLOT
15 " example" " the %#s value is %i" A 1+ SPRINTF A C!
A COUNT TYPE