Tuesday, July 23, 2013 0 comments
In addition to a file manager, operating systems also include utility programs that one can use to manage disks and files. The list of such programs is almost endless.
Disk Formatting: Disk formatting utility makes the disk ready to store data. Formatting creates a directory of the locations of each file called a file allocation table (FAT). When a user saves a file, the operating system stores it in a group of sectors, called cluster, the smallest storage unit the computer can address. To do so, it looks in the file allocation table for empty clusters and then stores the file in one of those locations. The address of the clusters where the file begins and the one where it ends are then listed in the file allocation table. When a user opens the file, the operating system uses those addresses to locate he clusters and open the file stored in them.
Fragmenting: When a user first uses a disk, data are laid down in a linear fashion. Each part of a file is stored in adjacent clusters. However, as a user begins to delete old files and add new ones, things begin to become less orderly, because fragments of files are scattered in clusters located in different areas on the disk. This file fragmentation shows the computer down because it takes longer for the drive to locate, save, and retrieve the fragmented files. To fix this problem, a user needs to regularly defragment or defrag the disk. This procedure is often overlooked by computer users, who then wonder why their system gets slower and slower as time goes by. In many eased, the system will even begin to misbehave; programs crash or files do not open. Often these problems can be fixed just by defragging the disk.
Disk scanning: A newly manufactured disk is not always perfect. Some areas of the disk may not be usable. The manufacturer scans the disk and electronically marks bad areas as unusable so that no data are stored there. As the user uses the disk, other areas may become bad. For this reason, a utility program is used to scan the disk at regular intervals to locate and mark any bad sectors. If this is not done, the operating system may store parts of a file in them and then the user will not be able to retrieve that part of the file. In addition, scanning finds and fixes problems with files. For example, when systems crash, parts of files may be left scattered on the disk and become lost. The disk scanning program locates these lost clusters and stores them together in a separate file. In some cases, a user can open these files and recover lost work.
File deletion and recycle bin: Many of the files created by users on a computer eventually become outdated and no longer needed. To remove these files from the disk, users delete them. On many newer operating systems, the procedure does not actually delete them from the disk. Instead, it moves them to a separate area of the disk called a recycle bin or trash can. If user decides later that she/he wants to recover the file, can open the recycle bin and restore it to the disk. When absolutely certain that the user will never need the files in the recycle bin; the user can make it empty. However, if a user ever deletes files, provided any subsequent commands did not place new files in the place on the disk where they are stored.