Any valid file number
A Long indicating the current read/write position
Returns the current position of the read/write marker in the open
The Seek function returns a whole number in the range 1 to 2,147,483,647.
filenumber was opened in Random mode,
the number returned by the Seek function refers
to the next record to be written or read.
In all other file open modes (Append, Binary, Input, and Output), the number returned by the Seek function is the byte position at which the next read or write operation will occur.