| Original author(s) | Tim Paterson |
|---|---|
| Developer(s) | Seattle Computer Products,Microsoft,Digital Research,IBM,Toshiba |
| Initial release | 1980; 45 years ago (1980) |
| Written in | MS-DOS:x86 assembly language |
| Operating system | 86-DOS,MS-DOS,PC DOS,FlexOS,4690 OS,PTS-DOS,SISNE plus,Windows,DR-DOS |
| Type | Command |
| License | MS-DOS:MIT |
Incomputing,sys is acommand used in manyoperating systemcommand-lineshells and also inMicrosoft BASIC.
SYS.COM (among other commands) inIBM PC DOS 1.0.SYS is an external command ofSeattle Computer Products86-DOS,[1]MicrosoftMS-DOS,IBMPC DOS,Digital ResearchFlexOS,[2]IBM/Toshiba4690 OS,[3]PTS-DOS,[4]Itautec/Scopus TecnologiaSISNE plus,[5] and MicrosoftWindows 9x operating systems. It is used to make an already formatted medium bootable. It will install aboot sector capable of booting the operating system into the first logical sector of the volume. Further, it will copy the principal DOS system files, that is, the DOS-BIOS (IO.SYS orIBMBIO.COM) and the DOSkernel (MSDOS.SYS orIBMDOS.COM) into the root directory of the target. Due to restrictions in the implementation of theboot loaders in the boot sector and DOS' IO system, these two files must reside in the first two directory entries and be stored at the beginning of the data area under MS-DOS and PC DOS. Depending on version, the whole files or only a varying number of sectors of the DOS-BIOS (down to only three sectors in modern issues of DOS) will have to be stored in one consecutive part. SYS will try to physically rearrange other files on the medium in order to make room for these files in their required locations. This is why SYS needs to bypass the filesystem driver in the running operating system. Other DOS derivatives such asDR-DOS do not have any such restrictions imposed by the design of the boot loaders, therefore under these systems, SYS will install a DR-DOS boot sector, which is capable of mounting the filesystem, and can then simply copy the two system files into the root directory of the target.SYS will also copy thecommand lineshell (COMMAND.COM) into the root directory.[6] Thecommand can be applied tohard drives andfloppy disks to repair or create a boot sector.
Although an article on Microsoft's website says theSYS command was introduced inMS-DOS version 2.0,[7] this is incorrect. SYS actually existed in86-DOS 0.3 already. According toThe MS-DOS Encyclopedia, the command was licensed toIBM as part of the first version of MS-DOS,[8] and as such it was part of MS-DOS/PC DOS from the very beginning (IBM PC DOS 1.0 and MS-DOS 1.25).
DR DOS 6.0 includes an implementation of theSYS command.[9]
The commandsyntax is:
SYS [drive1:][path] drive2:
Arguments:
[drive1:][path] – The location of the system filesdrive2: – The drive to which the files will be copiedC:\>sys a:SYS is also a command in Microsoft BASIC used to execute amachine language program in memory. The command took the formSYS n wheren is amemory location where the executable code starts.Home computer platforms typically publicised dozens ofentry points to built-in routines (such as Commodore'sKERNAL[10]) that were used by programmers and users to access functionality not easily accessible through BASIC.
