This function changes the size of a native file. 

Y is a negative integer tie number associated with a tied native file. 

X is a single integer value that specifies the new size of the file in bytes.  If X is smaller than the current file size, the file is truncated.  If X is larger than the current file size, the file is extended and the value of additional bytes is undefined.

The shy result of ⎕NRESIZE is the tie number of the resized file.