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 holder (10) is disclosed for storing books and similar articles and for supporting the articles in open position includes a body (14) and a cover (16) hinged together to define a right rectangular polyhedron shape when the holder is closed. The cover (16), which forms the upper portion of the holder (10), is pivotable forwardly and downwardly about a pair of double-acting hinges (18) located along a horizontal centerline on the front wall of the holder (10). The cover (16) includes a top wall …

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 …

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…

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…

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 and system for recording debug commands as they are executed on a program is disclosed. The line number in the program reached after executing the debug command is also stored on the tape. The debug history tape is a sequential record of the debug commands. A user may reexecute one or more of the debug commands on the program by running the debug history tape. The user may stop the reexecution of the debug commands on a given line in the program generally in the area thought to contain …

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…

A method and system for allowing both operating system buffers and application program buffers to reside in expanded memory is provided. In a preferred embodiment, a page frame in conventional memory is provided through which pages in expanded memory are accessed. An application program allocates pages in expanded memory and maps pages into the page frame. An operating system also allocates pages in expanded memory. In a preferred embodiment, an application program maps its allocated pages into …