PFE-SPRINTF PFE-PRINTF PICK
PFE-SPRINTF
* PFE-SPRINTF ( args ... format$ dest$ -- len-dest )

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

EXTENSIONS useful ordinary primitive