This sets the default input folder to 〈 fold〉. This folder is used to
find all input paths that do not explicitly specify a folder. For
example, if you specify `-di e:\r', then the input path
`src\myprog.c' would refer to the file `
e:\r\src\myprog.c', but the name `
d:\yourprog.c' would still refer to drive d. If the `
-di' switch is not given, TOS's ``current working directory" is used
instead. This is folder containing the file KEY.TTP unless you are
using a shell that lets you set the working directory to something
else.