The FDISK command manipulates hard disk partition tables. The name derives from IBM's habit of calling hard drives fixed disks. FDISK has the ability to display information about, create, and delete DOS partitions or logical DOS drive. It can also install a standard master boot record on the hard drive.
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It used 14" fixed disks (30 or 60MB) and could support up to two; RAM (main storage) ranged from 128KB to 512 KB. One 8" floppy diskette drive was built in. The 5362 also allowed the use of a channel attached external desktop 9332-200, 400, & 600 DASD, effectively allowing a maximum of 720MB.
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Even if the removable disks' capacity is smaller than fixed disks, their interchangeability guarantees a nearly unlimited quantity of data close at hand. Magnetic tape provided archival capability for this data, at a lower cost than disk. Many second-generation CPUs delegated peripheral device communications to a secondary processor. For example, while the communication processor controlled card reading and punching, the main CPU executed calculations and binary branch instructions.
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The last instruction executed in the BIOS code will be a "jump" to that address in order to direct execution to the beginning of the MBR copy. The primary validation for most BIOSes is the signature at offset , although a BIOS implementer may choose to include other checks, such as verifying that the MBR contains a valid partition table without entries referring to sectors beyond the reported capacity of the disk. To the BIOS, removable (e.g. floppy) and fixed disks are essentially the same.
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IBM introduced the IBM 3370 Direct Access Storage Device in January 1979 for IBM 4331, 4341, and System/38 midrange computers. It has seven fixed disks, and each unit has a capacity of 571 MB. It was the first HDD to use thin-film head technology; research on that technology started at Thomas J. Watson Research Center in the late 1960s. The 3370 was a fixed-block architecture device, used on DOS/VSE and VM, the only S/370 operating systems that supported FBA devices.
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But the M-JPEG data rate was too high for systems like Avid/1 on the Mac and Lightworks on PC to store the video on removable storage. The content needed to be stored on fixed hard disks instead. The secure tape paradigm of keeping your content with you was not possible with these fixed disks. Editing machines were often rented from facilities houses on a per-hour basis, and some productions chose to delete their material after each edit session, and then ingest it again the next day to guarantee the security of their content.
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A master boot record (MBR) is a special type of boot sector at the very beginning of partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept of MBRs was publicly introduced in 1983 with PC DOS 2.0. The MBR holds the information on how the logical partitions, containing file systems, are organized on that medium. The MBR also contains executable code to function as a loader for the installed operating system—usually by passing control over to the loader's second stage, or in conjunction with each partition's volume boot record (VBR).
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When the regulator is opened, steam forces the loose valve bodies against their respective fixed discs, and they then act as units similar to ordinary piston valves. When steam is shut off, the loose valve heads become detached from their respective discs and remain in their idle positions near the centre of the steam chest, while the valve spindle and fixed disks continue their reciprocating motion with the spindle sliding freely through the now stationary loose valve heads, and with the steam and exhaust ports now in communication. With both ends of the cylinders now in communication, the use of ordinary by-bass or snifting valves became unnecessary. Further similar experiments were carried out on Class 5B no.
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For mass storage, the System/3 used the IBM 5444 single-platter disk,System/3, IBM engineering announcement roughly the size of a large pizza; initially each platter held 2.5 MB of data. Standard configuration for storage was one or two fixed disks, each in a separate pull-out drawer, which typically held the operating system and user-developed programs. Additionally, each fixed disc could have a removable cartridge disk attached; these typically contained the data-files associated with various applications, for example Payroll, and users frequently had a number of them. Thus the low-end systems could support a maximum of 10 MB of online storage (two fixed, two removable), although in practice this was very expensive and not common.
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Trofimoff valve, closed Trofimoff valve, open The Trofimoff piston valve consisted of two fixed discs secured to the valve spindle, and two junk rings, each carrying a bull ring and four valve rings and both free to move longitudinally on the spindle. When the regulator is opened, steam forces the loose valve bodies against their respective fixed discs and they then act as units, similar to ordinary piston valves. When steam is shut off, the loose valve heads become detached from their respective discs and remain in their idle positions near the centre of the steam chest, while the valve spindle and fixed disks continue their reciprocating motion with the spindle sliding freely through the now stationary loose valve heads, and with the steam and exhaust ports now in communication.
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