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Upper Memory Area
In DOS memory management, the upper memory area (UMA) is the memory between the addresses of 640 KB and 1024 KB ( 0xA0000–0xFFFFF) in an IBM PC or compatible. IBM reserved the uppermost 384 KB of the 8088 CPU's 1024 KB address space for BIOS ROM, Video BIOS, Option ROMs, video RAM, RAM on peripherals, memory-mapped I/O, and obsoleted ROM BASIC. However, even with video RAM, the ROM BIOS, the Video BIOS, the Option ROMs, and I/O ports for peripherals, much of this 384 KB of address space was unused. As the 640 KB memory restriction became ever more of an obstacle, techniques were found to fill the empty areas with RAM. These areas were referred to as upper memory blocks (UMBs). Usage The next stage in the evolution of DOS was for the operating system to use upper memory blocks (UMBs) and the high memory area (HMA). This occurred with the release of DR DOS 5.0 in 1990. DR DOS' built-in memory manager, EMM386.EXE, could perfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM PC Memory Areas
International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is a publicly traded company and one of the 30 companies in the Dow Jones Industrial Average. IBM is the largest industrial research organization in the world, with 19 research facilities across a dozen countries; for 29 consecutive years, from 1993 to 2021, it held the record for most annual U.S. patents generated by a business. IBM was founded in 1911 as the Computing-Tabulating-Recording Company (CTR), a holding company of manufacturers of record-keeping and measuring systems. It was renamed "International Business Machines" in 1924 and soon became the leading manufacturer of Tabulating machine, punch-card tabulating systems. During the 1960s and 1970s, the IBM mainframe, exemplified by the IBM System/360, System/360 and its successors, wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EMM386
EMM386 is the expanded memory manager of Microsoft's MS-DOS, IBM's PC DOS, Digital Research's DR-DOS, and Datalight's ROM-DOS which is used to create expanded memory using extended memory on Intel 80386 CPUs. There also is an EMM386.EXE available in FreeDOS. Overview EMM386.EXE can map memory into unused blocks in the upper memory area (UMA), allowing device drivers and terminate-and-stay-resident programs to be "loaded high", preserving conventional memory. The technique probably first appeared with the development of CEMM, included with Compaq's OEM MS-DOS for the Compaq Deskpro 386 in 1986. Microsoft's version first appeared, built-in, with Windows/386 2.0 in 1987 and as standalone EMM386.SYS with MS-DOS 4.0 in 1988; the more flexible EMM386.EXE version appeared in MS-DOS 5.0 in 1991. EMM386 uses the processor's virtual 8086 mode. This forces memory accesses made by DOS applications to go through the processor's MMU (introduced in the 386), and the page table entr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Control Program Interface
In computing, the Virtual Control Program Interface (VCPI) is a specification published in 1989 by Phar Lap Software that allows a DOS program to run in protected mode, granting access to many features of the processor not available in real mode. It was supplanted by DOS Protected Mode Interface (DPMI) shortly after being introduced, due in large part to VCPI's inability to work in Windows 3.0's protected mode. Overview Developed since 1987 in cooperation with Quarterdeck Office Systems and with support by A.I. Architects, Lotus Development Corp., Quadram, Qualitas and Rational Systems, VCPI is provided by an expanded memory manager in DOS (e.g. CEMM, QEMM, later EMM386) and does allow 80386 protected-mode DOS extenders to coexist with 80386 EMS expanded memory emulators. It was eclipsed by DPMI, most notably because it was not supported for DOS programs run in Windows 3.0's native protected mode (called ''386 enhanced mode'') and because VCPI runs programs in Ring 0, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual 8086 Mode
In the 80386 microprocessor and later, virtual 8086 mode (also called virtual real mode, V86-mode, or VM86) allows the execution of real mode applications that are incapable of running directly in protected mode while the processor is running a protected mode operating system. It is a hardware virtualization technique that allowed multiple 8086 processors to be emulated by the 386 chip. It emerged from the painful experiences with the 80286 protected mode, which by itself was not suitable to run concurrent real-mode applications well. John Crawford developed the Virtual Mode bit at the register set, paving the way to this environment. VM86 mode uses a segmentation scheme identical to that of real mode (for compatibility reasons), which creates 20-bit linear addresses in the same manner as 20-bit physical addresses are created in real mode, but are subject to protected mode's memory paging mechanism. Overview The virtual 8086 mode is a mode for a protected-mode task. Conseq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Windows 95
Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged Microsoft's formerly separate MS-DOS and Microsoft Windows products into a single product and featured significant improvements over its predecessor, most notably in the graphical user interface (GUI) and in its simplified "plug-and-play" features. There were also major changes made to the core components of the operating system, such as moving from a mainly cooperatively multitasked 16-bit architecture of its predecessor Windows 3.1 to a 32-bit preemptive multitasking architecture. Windows 95 introduced numerous functions and features that were featured in later Windows versions, and continue in modern variations to this day, such as the taskbar, the notification area, file shortcuts on the desktop, plug and play driver integration, remov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MSCDEX
MSCDEX or Microsoft CD-ROM Extensions is a software program produced by Microsoft and included with MS-DOS 6.x and certain versions of Windows to provide CD-ROM support. Earlier versions of MSCDEX since 1986 were installable add-ons for MS-DOS 3.1 and higher. Overview The program is a driver executable which allows DOS programs to recognize, read, and control CD-ROMs using the High Sierra and – since version 2.0 as of 1988 – also the ISO 9660 file systems. This requires the previous loading of an appropriate CD-ROM device driver (example: OAKCDROM.SYS), usually from CONFIG.SYS. The final version of the MSCDEX program was 2.25, included with Windows 95 and used when creating bootable floppy disks with CD-ROM support. Starting with Windows 95, CD-ROM access became possible through a 32-bit CDFS driver. The driver uses the Microsoft networks interface in MS-DOS. This is the reason that at least version 3.1 of MS-DOS is required. The driver essent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OSI Model
The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." In the OSI reference model, the components of a communication system are distinguished in seven abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. The model describes communications from the physical implementation of transmitting bits across a transmission medium to the highest-level representation of data of a distributed application. Each layer has well-defined functions and semantics and serves a class of functionality to the layer above it and is served by the layer below it. Established, well-known communication protocols are decomposed in software development into the model's hierarchy of function calls. The Internet protocol suite as defined in and is a model of net ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terminate-and-stay-resident
A terminate-and-stay-resident program (commonly TSR) is a computer program running under DOS that uses a system call to return control to DOS as though it has finished, but remains in computer memory so it can be reactivated later. This technique partially overcame DOS's limitation of executing only one program, or task (computing), task, at a time. TSRs are used only in DOS, not in Microsoft Windows, Windows. Some TSRs are utility software that a computer user might call up several times a day, while working in another program, by using a keyboard shortcut, hotkey. Borland Sidekick was an early and popular example of this type. Others serve as device drivers for computer hardware, hardware that the operating system does not directly support. Use Normally DOS can run only one program at a time. When a program finishes, it returns control to DOS using the system call of the DOS API. The memory and system resources used are then marked as unused. This makes it impossible to restar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MEMMAKER
This article lists notable commands provided by the MS-DOS disk operating system (DOS), especially as used on an IBM PC compatible computer. Other DOS variants as well as the legacy Windows shell, Command Prompt (cmd.exe), provide many of these commands. Many other DOS variants are informally called ''DOS'', but are not included in the scope of the list. The highly related variant, IBM PC DOS, is included. The list is not intended to be exhaustive, but does include commands covering the various releases. Each command is implemented either as built-in to the command interpreter, COMMAND.COM, or as an external program. Although prevailing style is to write command names in all caps, the interpreter matches ignoring case. Commands APPEND Sets the path to be searched for data files or displays the current search path. The APPEND command is similar to the PATH command that tells DOS where to search for program files (files with a .COM, . EXE, or .BAT file name extension). The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MS-DOS 5
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS" (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatibles during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system. IBM licensed and re-released it in 1981 as PC DOS 1.0 for use in its PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax and capabilities. Beginning in 1988 with DR-DOS, se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft
Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The early 1980s and home computers, rise of personal computers through software like Windows, and the company has since expanded to Internet services, cloud computing, video gaming and other fields. Microsoft is the List of the largest software companies, largest software maker, one of the Trillion-dollar company, most valuable public U.S. companies, and one of the List of most valuable brands, most valuable brands globally. Microsoft was founded by Bill Gates and Paul Allen to develop and sell BASIC interpreters for the Altair 8800. It rose to dominate the personal computer operating system market with MS-DOS in the mid-1980s, followed by Windows. During the 41 years from 1980 to 2021 Microsoft released 9 versions of MS-DOS with a median frequen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
