Open, Close and Rewind

The routine uvopen opens a uv data set and readies it for access. Here dataname is a string giving the data set's name. Status can be either 'old' or 'new', depending whether an old data set is being read, or a new data set is being created. Tno is an integer handle passed back by the open routine (and is used for all future access to the data set). The routine uvclose closes the data set. The routine uvrewind positions a uv file at its beginning, and allows it to be read again.