Unlike conventional PCs, these devices contain no hard disk or operating system.
From the businessweek.com
AmigaDOS provides the disk operating system portion of the AmigaOS.
From the en.wikipedia.org
A decade ago, the two companies teamed up to develop the IBM PC, with Microsoft contributing the disk operating system, or DOS.
From the time.com
Most home computers had a primary OS and BASIC stored as ROM, with the option of loading a more advanced disk operating system from a floppy disk.
From the en.wikipedia.org
It took him less than half an hour to familiarize himself with the TRS-80 disk operating system, the master program that tells a computer how to store and retrieve data.
From the time.com
The development of GLaDOS, an artificially intelligent research assistant and disk-operating system, began in 1986 in response to Black Mesa's work on similar portal technology.
From the en.wikipedia.org
Finally I had to reformat the hard disk, reload the operating system and begin anew.
From the newsobserver.com
You will have to first boot the computer up from the operating system disk.
From the online.wsj.com
This may occur during operating system installation, or when adding a new disk.