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Disk operating system

Operating system focused on disk-based file operations From Wikipedia, the free encyclopedia

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A disk operating system (DOS) is a computer operating system that provides storage access limited to disk hardware (such as a floppy, hard drive and optical)[disputed discuss] that today is obsolete. A DOS provides a file system and a means for loading and running programs stored on the disk. Typically, a DOS was loaded from the disk as part of the boot process. More complex and modern operating systems such as Windows and Unix-based are not considered a DOS.[citation needed][1]

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History

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Before modern storage such as the disk drive, floppy disk, and flash storage, early computers used storage such as delay line, core memory, punched card, punched tape, magnetic tape, and magnetic drum. Early microcomputers and home computers used paper tape, audio cassette tape (such as Kansas City standard), or no permanent storage at all. Without permanent storage, programs and data are input directly into memory using front panel switches, or is input through a computer terminal or keyboard, sometimes controlled by a BASIC interpreter in ROM. When power is turned off, all information is lost.

In the early 1960s, as disk drives became larger and more affordable, various mainframe and minicomputer vendors introduced disk operating systems and modified existing operating systems to use disks.

Hard disks and floppy disk drives require software to manage rapid access to block storage of sequential and other data. For most microcomputers, a disk drive of any kind was an optional peripheral. Systems could be used with a tape drive or booted without a storage device at all. The disk operating system component of the operating system was only needed when a disk drive was used.

By the time IBM announced the System/360 mainframes, the concept of a disk operating system was well established. Although IBM did offer Basic Programming Support (BPS/360) and TOS/360 for small systems, they were out of the mainstream and most customers used either DOS/360 or OS/360.

Most home and personal computers of the late 1970s and 1980s used a disk operating system; most often with "DOS" in the name and simply referred to as "DOS" in the context of its user community. For example, CBM DOS, Atari DOS, TRS-DOS, Apple DOS, Apple ProDOS, and MS-DOS. CP/M is also a disk operating system, despite not having "DOS" in the name.[2]

A DOS is usually loaded from a disk, but there are exceptions, such as Commodore's disk drive for the Commodore 64 and VIC-20 which contain the DOS in ROM. Some versions of AmigaDOS mostly resides in ROM, as a part of a Kickstart firmware.

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OS extensions

  • Commodore DOS is on 8-bit Commodore computers such as the Commodore 64. Unlike most other DOS systems, it is integrated into the disk drives, not loaded into the computer's own memory.
  • Atari DOS is used by the Atari 8-bit computers. The Atari OS only offers low-level disk-access, so an extra layer called DOS can be booted from a floppy for higher level functions such as filesystems.[3] Third-party replacements for Atari DOS include DOS XL, SpartaDOS, MyDOS, TurboDOS, and Top-DOS.
  • MSX-DOS is for the MSX computer standard. The initial version, released in 1984, is MS-DOS 1.0 ported to Z80. In 1988, version 2 has facilities such as subdirectories, memory management, and environment strings. The MSX-DOS kernel resides in ROM (built-in on the disk controller) so basic file access capacity is available even without the command interpreter, by using BASIC extended commands.
  • Disc Filing System (DFS) is an optional component for the Acorn BBC Micro, as a kit with a disk controller chip, a ROM chip, and a few logic chips, to be installed inside the computer.
  • Advanced Disc Filing System (ADFS) is a successor to Acorn's DFS.
  • AMSDOS is for the Amstrad CPC computers.
  • GDOS and G+DOS is for the +D and DISCiPLE disk interfaces for the ZX Spectrum.
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Main OSes

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Some disk operating systems are the operating systems for the entire computer system.

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See also

References

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