This function returns the length of an opened file in number of records. The argument of the function has to be the file number that was used by the statement OPEN to open the file.
The actual number of records is calculated using the record size specified when the command OPEN was used. The returned number is the number of records that fit in the file. If the file is longer containing a fractional record at the end the fractional record is not counted.
If there was no record length specified when the file was opened the length of the file is returned in number of bytes. In this case fractional record has no meaning.