what is the main purpose of the hard drive
Hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk,[b] is an electromechanical data storage device that uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks (platters) coated with magnetic material. The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces.[2] Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order and not only sequentially. HDDs are a type of non-volatile storage, retaining stored data even when powered off.[3][4][5]
Computer data storage Data are encoded by assigning a bit pattern to each character, digit, or multimedia object. Many standards exist for encoding (e.g., character encodings like ASCII, image encodings like JPEG, video encodings like MPEG-4).
Hard disk drive HDD data transfer rate depends upon the rotational speed of the platters and the data recording density. Because heat and vibration limit rotational speed, advancing density becomes the main method to improve sequential transfer rates. Higher speeds require a more powerful spindle motor, which creates more heat. While areal density advances by increasing both the number of tracks across the disk and the number of sectors per track,[113] only the latter increases the data transfer rate for a given rpm. Since data transfer rate performance tracks only one of the two components of areal density, its performance improves at a lower rate.[citation needed]
Solid-state drive A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies as memory to store data persistently. It is also sometimes called solid-state disk;[1] the word "disk" is inappropriate since SSDs do not have physical disks. SSDs primarily use traditional hard disk drive (HDD) interfaces, such as SATA and SAS, greatly simplfying usage of SSDs in computers.[2] Following the initial acceptance of SSDs with HDD interfaces, new I/O interfaces like M.2 and U.2 have been designed to address specific requirements of the Flash memory technology used in SSDs.