The turbo

Part 2 Chapter 18 Files
Now, to save the information in Ship, you could write:
Assign(ShipFlle,'SHIPS.DAT');
Rewrite(ShipFlle );
Write( ShipFlle,Ship);
Close(ShipFlle);
Simple, isn't it? With a single Write statement, you have sent all
the ship records out to the disk. To read it back in, you just write:
Assign(ShipFlle,'SHIPS.DAT');
ResetCShipFile);
Read(Ship:B'ile,Ship );
Close(ShipFile);
Unfortunately, you've now lost track of one piece of information,
namely the value of ShipCnt. However, there are a number of
ways around this. First, you could redefine ShipArray to be a
record with two fields: the ship count and the array itself. Second,
you could save the value of ShipCnt in another file, either by itself
or as part of another data structure. Third, you could add another
field to the definition of AShip which would indicate whether or
not that record was, indeed, a "real" ship; then, after you've read
Ship in, you just go through and count all of the records with that
value set. Finally, you could rewrite the game so that the value
ShipCnt is no longer needed.
18.1 RANDOM ACCESS OF FILES
From what you've seen so far, to read or write a particular record
in a file, you must go to the start of the file and work from there. If
you wish to read the 10th record in a file, you must reset the file
and go through the first nine records to get to the tenth. If you
want to modify the tenth record, you must read it in as mentioned,
reset the file, read in the first nine, then write the 10th back out. In
short, a lot of work.
18-5