Type: External (1.0 and later)
SYS [source] d:
Purpose: Transfers the operating system files to another disk. The three files that are transferred are IO.SYS, MSDOS.SYS, and COMMAND.COM (if you are using IBM's version of DOS, they are named IBMIO.SYS, IBMDOS.SYS, and COMMAND.COM).
Using versions of DOS prior to version 4, the disk had to have enough contiguous free
space on it for the three files to be transferred. In the newer versions that is no longer
You may not be able to reliably transfer system files to a disk that already has a different version of DOS on it.
The system files IO.SYS and MSDOS.SYS are hidden files that do not appear when you use the DIR command to display a directory of a system disk.
In versions of DOS prior to version 5, when you use the SYS command to transfer the system files to a disk, the file COMMAND.COM (which contains the command processor) is not transferred. When using those earlier versions, you must use the COPY command to transfer COMMAND.COM.
A system disk can also be transferred (along with all the files stored on it) using the DISKCOPY command.
If an error is encountered, SYS will not transfer the system files. DOS will report one of the following error messages:
Message: No room for system on target disk
Meaning: This message means that there is not enough room on the target disk for the system files.
Message: Incompatible system size
Meaning: The system files do not take up the same amount of space on the target disk as the new system will need. This can happen if you try to transfer system files to a disk that already has a different version of DOS on it.
You may receive other error messages if DOS cannot find the required system files at the source location specified or if you try to use the SYS command to transfer the system files to compressed drives or networked drives.