An improved method and system for transferring control in a multitasking computer system is provided. In preferred embodiments for use with 80386 machines, the virtual machine monitor (VMM) writes a virtual machine break point (VMBP) instruction into the executable code of selected DOS routines to cause the DOS routines to transfer control to the VMM. By selecting systems calls of indefinite duration for the application of this method, system performance can be improved. In this preferred embodi…

An improved peripheral device for a computer wherein the improvement comprises circuitry which derives power for the peripheral device from the control and data signal lines interconnecting the peripheral device to the computer. Preferably, the peripheral device is a mouse which uses a microprocessor to translate signals received from a pair of encoders. Power for the microprocessor is derived from a pair of control lines through the use of a voltage reference setting zener diode, a polarity mai…

Improved methods and operating systems for use with a multi-mode microprocessor enable efficient operation in a multi-mode environment. Preferred embodiments for use with microprocessors which were not designed to switch from each mode to another mode enable multi-tasking of a mixture of programs written for different modes using the mode switching methods of the present invention. Frequently used portions of the operating system are stored in memory at locations which can be commonly addressed …

A method and system of displaying a monochrome bitmap on a color display. In a preferred embodiment, a system according to the present invention accomplishes the display of the monochrome bitmap in any two preselected colors. The multibit representations for the two preselected display colors are compared to identify bitmap planes having common bit values for each color. The input for logic units for the identified planes are then forced to 0. The latch registers for each plane of the bitmap mem…

A method of compressing a text file in digital form is disclosed. A full text file having characters formed into phrases is provided by an author. The characters are digitally represented by bytes. A first pass compression is sequentially followed by a second pass compression of the text which has previously been compressed. A third or fourth level compression is serially performed on the previously compressed text. For example, in a first pass, the text is run-length compressed. In a second pas…

Improved methods and operating systems for use with a multi-mode microprocessor enable efficient operation in a multi-mode environment. Preferred embodiments for use with microprocessors which were not designed to switch from each mode to another mode enable multi-tasking of a mixture of programs written for different modes using the mode switching methods of the present invention. Frequently used portions of the operating system are stored in memory at locations which can be commonly addressed …

A method and apparatus for notifying programs that a logical event has occurred on a network, said event being a power failure. Upon the occurrence of a logical event in an operating program, an alert report is generated and stored in a buffer. An alert function call occurs, providing the event type and a pointer to the buffer. The alert function call reads a look-up table listing the programs or users requesting notification of events. The look-up table provides the addresses to which notificat…

The disclosure relates to a mouse for use as a peripheral device in conjunction with a host computer wherein power for driving the circuitry of the mouse is obtained directly from signal lines interconnecting the mouse and the host computer.

A method and apparatus for filling an area of a computer display with a preselected color is provided. Typical computer systems software provides the capability to represent 256 different intensities of a color. However, many color displays cannot support the displaying of 256 intensity levels. The present invention provides a method and apparatus for mapping the higher number of intensity levels supported by the systems software to the lower number of intensity levels actually supported by the …

A method and system for allowing an interrupted computer program to detect the occurrence of an interrupt. In a preferred embodiment, a system according to the present invention allows an Intel 80286-compatible based computer program executing in real mode to detect the occurrence of an interrupt during the execution of a set of instructions. According to a preferred method of the present invention, the LOADALL instruction is used to load the code segment selector with the segment address of the…