Storage devices

Types of HDD

Types of Mobile HDD

Partition Series

FAT

NTFS

Raid

Linux

Other Parts

Operating Systems

Windows

Other operating systems

Other

Appendix D. Glossary

  • Active partition. One of the primary partitions of a hard disk is usually active. Default MBR code tries to boot an operating system from the active partition of the first hard disk. Letter assignment in Microsoft operating systems depends on what partitions are active.

    Bad cluster. A cluster that contains bad sectors. Such cluster cannot store useful information.

    Bad sector. A sector that cannot store the information written, for instance due to defects or aging of the magnetic surface.

    BIOS extension. BIOSes that were released before 1994 could only support hard disks that were less than 8 gigabytes. Extended hard disk management functions were added to BIOSes to solve this problem, and now the maximum supported hard disk capacity is 275 bytes.

    Boot partition of an operating system is a partition from which the initial stage of operating system booting is done (boot sector is read and executed, first file of the operating system is read and executed).

    Boot record . The initial part of a partition that contains code and data necessary for booting an operating system. May consist of one or several sectors. First sector of a boot record must end with the boot sector signature (0AA55h).

    Boot sector is the first sector of a disk or a partition that contains the initial code for the operation system booting. Boot sector must end with 0AA55h signature.

    Bootable disk is a disk from which an operating system may be booted. A bootable disk must contain a boot sector of an operating system and the necessary system and configuration files. The «Bootable disk» term usually refers to diskettes and CD-ROMs.

    Bootable partition . A partition that can host an operating system. In the beginning of such a partition there should be a boot record.

    Booting an operating system is initialized by reading its boot sector to the memory at 0:7C00h and passing control to it. Since each operating system has its own boot sector, it is able to perform the required actions on loading and initializing system and configuration files.

    Boot the computer is a procedure that is executed every time a computer is turned on or an operating system finishes its work or when the reset button is pressed. Booting consists of the following stages:
    • Hardware diagnostics
    • Memory check
    • Built-in BIOS initialization
    • Initialization of additional hardware components and their BIOSes (video, SCSI etc.)
    • Booting an operation system

    Cluster . Information storage unit in such file systems as FAT and NTFS. Every file occupies a certain number of whole clusters, so the more the cluster size the higher the losses are that are due to file size adjustment, but the smaller the cluster the larger the cluster distribution tables.

    Cylinder . A group of all the tracks on all the magnetic platters of a hard disk that can be accessed without moving the magnetic head. Access to the data inside one cylinder is much faster than moving the head from one cylinder to the other.

    Disk . It is a general term that can mean both a data storage media (floppy disk, compact disk), and a data-reading device (hard disk), and a partition that is accessible from some operating system (logical disk).

    Diskette . Floppy disk. A removable storage media that consists of a flexible magnetic platter enclosed in a protective envelope. Nowadays the most common are 3"5 diskettes with 1.44 megabyte capacity.

    File . A file is named information storage in the file system. In different file systems files can be stored in different ways, different may also be ways to store file names and to write the full path to the file in the folder tree.

    FAT (File Allocation Table) . FAT is a table for dynamic disk space allocation for files in MS-DOS and Windows operating systems. A cluster is a unit of allocated space, it consist of one or several sectors. FAT contains a number of cluster and service information about its condition (for example, bad, free).

    File system . Data structure that is necessary to store and manage files. File system does the following functions: tracks free and occupied space, supports folders and file names, tracks the physical positions of files on the disk. Each partition may be formatted with its own file system.

    Folder . A table in the file system that contains description of files and other folders. Such structure allows creating folder tree that begins with the root folder.

    Formatting . The process of creating service structure on the disk. There are three levels of hard disk formatting: low-level (marking the magnetic surface with tracks and sectors), partitioning and high-level (creation of file system on a partition).

    Hard disk . Fixed storage media along with integrated electronics that consists of several magnetic platters that rotate synchronously on one spindle. Hard disks have relatively high capacity and high read/write speed.

    Hard disk geometry . A set of hard disk parameters that usually includes the number of cylinders, heads and sectors per track.

    Head (magnetic head, read/write head). A hard disk consists of several magnetic platters, for each side of each platter there is a head that is used to read and write information on it.

    Hidden partition . A partition that is somehow made invisible to the operating system. Usually partitions are hidden by changing their type.

    Label . An optional name that can be assigned to a partition to simplify its identification. Usually has the same limitation as file names. For example, FAT partitions have labels up to 11 characters long, but may contain spaces.

    Letter (of a drive, partition). All operating systems that are somehow DOS-compatible use Latin letters to identify drives and partitions. Letters A: and B: are usually reserved for floppy drives. Starting with C: letters are assigned to hard disk partitions that can be recognized by the operating system. Separate letters may be assigned to CD-ROMs, to other disk drives and to network drives.

    Logical disk is a partition whose file system is recognized by the operating system. Usually each logical disk is assigned with a letter that uniquely identifies it.

    Logical partition . A partition information about which is located not in MBR, but in the extended partition table. The number of logical partitions on a disk is unlimited.

    Master Boot Record (MBR) is a special place in the very first sector of the hard disk to store information about the hard disk partitioning and code to be loaded with BIOS. All the actions that follow depend on the contents of this code.

    Operating system is a set of programs that usually includes kernel, drivers, shell, and system programs that is used for centralized hardware management and hiding the details of hardware management from the user and applications.

    Operating system installation is a process during which its system folders are created, system files are copied and boot sector is created.

    Partition . An independent area on a hard disk where a file system can be located. A partition can be either primary or logical, depending on its position in the partition structure. One of the primary partitions of a hard disk may be active. A partition has the following attributes: type, beginning and size. Besides, some partition managing software and boot managers allow hiding partitions. Information about partitions is stored in the partition table.

    Partition structure . All the partitions on a hard disk make a tree with the root in the MBR partition table. Many operating systems and programs assume that any partition table but MBR may contain not more than one partition entry and one table entry, and it simplifies the partition structure greatly - all the logical partitions form one chain.

    Partition table . It is the table that contains the information about partitions and links to other partition tables. A partition table cannot have more than four entries. Main partition table is located in the hard disk MBR, and the rest partition tables are called extended. Partition tables are usually stored in the first sector of a cylinder.

    Partitioning . The process of creating the partition logical structure on a hard disk. Partitioning is usually done with programs like FDISK. Disk administrator completely replaces FDISK where functionality is concerned and allows performing many more useful operations.

    Primary partition . The partition, information about which is contained in the MBR partition table. Majority of operating systems can be booted only from the primary partition of the first hard disk, but the number of primary partitions is limited.

    Physical disk . A disk that is physically a separate device. Thus, a floppy disk, hard disk, CD-ROM are physical disks.

    Rootfolder . The folder where the folder tree of a file system begins. Starting from the root folder one can uniquely describe the file position on the folder tree by sequentially naming all the intermediate nested folders, e.g.: \WINDOWS\SYSTEM\VMM32.VXD. Here the WINDOWS folder is a subfolder of the root folder, SYSTEM folder - of the WINDOWS folder, and the VMM32.VXD file is located in the SYSTEM folder.

    Sector . It is the minimal information unit on a disk that is transferred in single read or write operation. Usually a sector is 512 bytes large. A sector on a disk can be addressed two ways: via the absolute number or via cylinder, head, and sector number on a track.

    Status . A flag that shows if a partition is active. This flag is stored in the partition table and has no meaning for logical partitions.

    System disk/partition is a disk/partition from which an operating system may be booted. Such disk usually contains the boot sector and system files of this operating system.

    System file is a file that contains the code and constant data for an operating system. Each operating system has its own system file set.

    System folder . Some operating systems keep most of their files in a special folder on a partition that may be different from the system one. For example for Windows 95/98/ME operating systems IO.SYS system file resides on the system partition, while other system files are located in the system folder which is usually called WINDOWS. Program Files folder can also be treated as system since it resides on the same partition as WINDOWS and also contains files that are relevant to the operating system.

    Track . Disks are divided into concentric circles called tracks. Information from one track can be accessed without moving the head.

    User interface is a set of principles, concepts, and means by which programs interact with the user. For example in window interface all input and output is done in windows and the mouse is widely used.
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