Abstract: The UNIX.RTM. and MS-DOS.RTM. operating systems are supported in a multi-tasking computer. At the heart of the computer is a microprocessor having protected and non-protected modes. The computer includes special-purpose hardware which prevents the MS-DOS system and its applications, which execute in the non-protected mode, from interfering with the UNIX system and its applications, which execute in the protected mode. In particular, this hardware monitors addresses generated by the computer and, by selectively inhibiting the associated control pulses, prevents the MS-DOS system from, for example, writing in UNIX-system-allocated memory, or accessing I/O devices that the UNIX system is currently using. In addition, a context switching feature is provided whereby the user can select, via a keyboard operation, to have displayed on the computer video monitor at any given time the image generated from the current UNIX system screen data or the image generated from the current MS-DOS system screen data.
Type:
Grant
Filed:
October 9, 1985
Date of Patent:
May 24, 1988
Assignees:
American Telephone & Telegraph Company, AT&T Information Systems, Inc., Locus Computing Corporation
Inventors:
David R. Blanset, David A. Butterfield, Kenneth M. Keverian, Charles S. Kline, Gerald J. Popek
Abstract: The UNIX.RTM. and $MS-DOS sup R $ operating systems are supported in a multi-tasking computer. At the heart of the computer is a microprocessor having protected and non-protected modes. The computer includes special-purpose hardware which prevents the MS-DOS system and its applications, which execute in the non-protected mode, from interfering with the UNIX system and its applications, which execute in the protected mode. In particular, this hardware monitors addresses generated by the computer and, by selectively inhibiting the associated control pulses, prevents the MS-DOS system from, for example, writing in UNIX-system-allocated memory, or accessing I/O devices that the UNIX system is currently using. In addition, a context switching feature is provided whereby the user can select, via a keyboard operation, to have displayed on the computer video monitor at any given time the image generated from the current UNIX system screen data or the image generated from the current MS-DOS system screen data.
Type:
Grant
Filed:
October 9, 1985
Date of Patent:
May 10, 1988
Assignees:
American Telephone and Telegraph Company, AT&T Information Systems Inc., Locus Computing Corporation
Inventors:
David R. Blanset, David A. Butterfield, Kenneth M. Keverian, Charles S. Kline, Gerald J. Popek