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    Definitions 2 min read
    Hierarchical, or hierarchy, refers to systems that are organized in the shape of a pyramid. Items, such as objects, names, categories, or values, are represented as above, below, or at the same level as another item. Hierarchical systems are used in everyday life. For example, the army uses a hierarchy in that generals are at the top of the pyramid and privates are at the bottom. Similarly, the system for classifying plants and animals according to species, family, and genus is hierarchical. The term is derived from the Greek words hieros, meaning sacred, and archein, meaning rule or order.

    Hierarchy in computing

    File system hierarchy

    The most common type of hierarchy in computing is a file system, in which computer files are placed somewhere in a hierarchical tree structure. File systems have a top level that is referred to as the root of the file system. Under the root are subdirectories such as Program Files, Documents, and Setting. Under these subdirectories are more subdirectories.

    Memory hierarchy

    Similarly, computer memory ranks components in terms of response times. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and controlling technologies. There are four major memory storage levels:

    1. Internal: Such as processor registers and cache
    2. Main: Such as the system RAM and controller cards
    3. Online mass storage: Such as secondary storage
    4. Offline bulk storage: Such as tertiary and offline storage

    While this is a general memory hierarchy, there are other useful structures out there.

    Computer System Level Hierarchy

    Computer System Level Hierarchy (CSLH) is the combination of different levels that connect the computer with the user and that make use of the computer. In addition, it describes how the computational activities are performed on the computer and the elements used in different levels of the system. CSLH consists of seven levels:

    • Level 0: Related to digital logic
    • Level 1: Related to control
    • Level 2: Consists of machines
    • Level 3: Consists of system software
    • Level 4: Consists of assembly language
    • Level 5: Consists of high-level language
    • Level 6: Consists of users and executable programs.
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