Vfwrite writes a file to a vfloppy image.

usage: vfwrite <imageName> [<fileName>]

After checking the image is mounted properly, the file name is 
looked up in the image and if found the size is added to the
free space. If the total is larger than the new file size,
the image file is deleted and the new file is written to the
image. The number of free directory entries is checked too, but
this will not be an problem often. The image supports 64 entries
(each 16 kByte part of a file is an entry).

The specified file name can be upper of lower case, it is converted
CP/M standard upper case. The total length is truncated to eleven
characters (excluding an optional dot), and the extension (what's
behind the dot) to three. I did some testing on this part.

Fred Jan Kraan, 2002-08-19
