 three indicators. It should also be easy to see now how some of those wonderful appli- cations like Norton Utilities work. When you direct your computer to erase a file, it doesn't really erase it; it just removes the pointers so that it is no longer a "registered" file and can no longer be found on the hard drive. What file restore utilities do is remember where the pointers were when you told the computer to erase the file. That way, when you beg the computer to find the file after you've done something stupid (this is always the trick of killing the chicken and lighting candles), the utility has a trivial task: Simply restore the pointers. As long as there hasn't been too much disk activity since the deletion and the file hasn't been overwritten, it can be recovered. Another useful tool is the disk optimization utility. It keeps track of the files and applications that you, the user, accesses most often while at the same time keeping track of the degree of fragmentation that the files stored on the disk are experiencing. Think about it: When disks start to get full, there is less of a chance that the OS will find a single contiguous piece of writeable disk space and will therefore have to fragment the file before writing it to the disk. Disk optimization utilities perform two tasks. First, they rearrange files on the disk surface so that those accessed most frequently are written to new locations close to the spin- dle, which spins faster than the outer edge of the disk and, therefore, is accessible more quickly. Second, they rearrange the file segments and attempt to reassemble files or at least move them closer to each other SO that they can be more efficiently managed. OK, enough about hard drive anatomy. Other forms of secondary memory include those mentioned earlier-writeable CDs, DVDs, zip disks, floppies, and nonvolatile memory arrays. As I mentioned, this has become a big business because these products make it relatively easy for users to back up files and keep their systems running efficiently. Down