SYS (command line command)

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SYS is an external command line command in PC-compatible DOS and Windows 9x for creating or repairing bootable hard disks and floppy disks .

Working method

Assuming the disk is already formatted , the command installs bootable code into the boot sector , the first logical sector of the disk.

In addition, the two system files, the DOS BIOS ( IO.SYSor IBMBIO.COM) and the DOS kernel ( MSDOS.SYSor IBMDOS.COM) are copied to the main directory of the data carrier. Due to restrictions in the implementation of the boot loader , these two files must be the first two files in the main directory. In addition, up to MS-DOS or PC DOS 3.3 the contents of both files must be completely unfragmented at the top , with DOS 3.3 and 4.0 only the first three sectors of IO.SYS/ IBMBIO.COM. From DOS 5.0 onwards it was sufficient if at least the first three sectors of IO.SYS/ were IBMBIO.COMstored unfragmented somewhere in the data area. SYStherefore tries to rearrange any occupied sectors in the file system until the above conditions are met. For this reason it SYSdoes not work at the file system level, but accesses the sectors directly. DR-DOS does not have this problem, the DR-DOS boot loader is able to find the DOS BIOS and the kernel independently. SYSonly has to describe the boot sector there, the system files are simply copied into the main directory.

As of DOS 5.0, SYS also copies the command line interpreter COMMAND.COMand as of MS-DOS 6.0 or 6.2 DBLSPACE.BINorDRVSPACE.BIN into the main directory.

An article on the Microsoft website mentions that SYSMS-DOS 2.0 was introduced, which is actually incorrect. SYSwas already available in 86-DOS 0.3. According to The MS-DOS Encyclopedia , it was licensed SYSto IBM as part of the first version of MS-DOS and, as such, was part of IBM PC DOS 1.0 and MS-DOS 1.25.

See also

Individual evidence

  1. ↑ a b c Microsoft: SYS.COM Requirements in MS-DOS versions 2.0-6.0. April 12, 2015, accessed September 27, 2016.
  2. ^ Ray Duncan: The MS-DOS Encyclopedia . Microsoft Press, Redmond, Wash. 1988, ISBN 1-55615-049-0 , pp. 940 .

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