Real mode, also called real address mode, is an operating mode of all x86-compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20-bit segmented memory address space and unlimited direct software access to all addressable memory, I/O addresses and peripheral hardware. Real mode provides no support for memory protection, multitasking, or code privilege levels.
The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces (APIs) available in the Microsoft Windows operating systems. The name Windows API collectively refers to several different platform implementations that are often referred to by their own names. Almost all Windows programs interact with the Windows API. On the Windows NT line of operating systems, a small number use the Native API.
DJ's GNU Programming Platform (DJGPP) is a software development suite for Intel 80386-level and above, IBM PC compatibles which supports DOS operating systems. It is guided by DJ Delorie, who began the project in 1989. It is a port of the GNU Compiler Collection (GCC), and mostly GNU utilities such as Bash, find, tar, ls, GAWK, sed, and ld to DOS Protected Mode Interface (DPMI). Supported languages include C, C++, Objective-C/C++, Ada, Fortran, and Pascal.
In computing, the DOS Protected Mode Interface (DPMI) is a specification introduced in 1989 which allows a DOS program to run in protected mode, giving access to many features of the new PC processors of the time not available in real mode. It was initially developed by Microsoft for Windows 3.0, although Microsoft later turned control of the specification over to an industry committee with open membership. Almost all modern DOS extenders are based on DPMI and allow DOS programs to address all memory available in the PC and to run in protected mode.
In DOS memory management, extended memory refers to memory above the first megabyte (220 bytes) of address space in an IBM PC or compatible with an 80286 or later processor. The term is mainly used under the DOS and Windows operating systems. DOS programs, running in real mode or virtual x86 mode, cannot directly access this memory, but are able to do so through an application programming interface called the Extended Memory Specification (XMS). This API is implemented by a driver (such as HIMEM.SYS) or the operating system, which takes care of memory management and copying memory between conventional and extended memory, by temporarily switching the processor into protected mode. In this context, the term "extended memory" may refer to either the whole of the extended memory or only the portion available through this API.
In DOS memory management, expanded memory is a system of bank switching that provided additional memory to DOS programs beyond the limit of conventional memory (640 KiB).
In DOS memory management, conventional memory, also called base memory, is the first 640 kilobytes of the memory on IBM PC or compatible systems. It is the read-write memory directly addressable by the processor for use by the operating system and application programs. As memory prices rapidly declined, this design decision became a limitation in the use of large memory capacities until the introduction of operating systems and processors that made it irrelevant.
Windows Console is the infrastructure for console applications in Microsoft Windows. An instance of a Windows Console has a screen buffer and an input buffer. It allows console apps to run inside a window or in hardware text mode. The user can switch between the two using the Alt+↵ Enter key combination. The text mode is unavailable in Windows Vista and later. Starting with Windows 10, however, a native full-screen mode is available.
The Microsoft Macro Assembler (MASM) is an x86 assembler that uses the Intel syntax for MS-DOS and Microsoft Windows. Beginning with MASM 8.0, there are two versions of the assembler: One for 16-bit & 32-bit assembly sources, and another (ML64) for 64-bit sources only.
Virtual DOS machines (VDM) refer to a technology that allows running 16-bit/32-bit DOS and 16-bit Windows programs when there is already another operating system running and controlling the hardware.
CEMM, for Compaq Expanded Memory Manager was the first so-called PC "memory manager" for Intel 80386 CPUs, able to provide expanded memory (EMS) emulation by using the virtual memory features and the virtual 8086 mode of the CPU.
A DOS extender is a computer software program running under DOS that enables software to run in a protected mode environment even though the host operating system is only capable of operating in real mode.
The architecture of Windows NT, a line of operating systems produced and sold by Microsoft, is a layered design that consists of two main components, user mode and kernel mode. It is a preemptive, reentrant multitasking operating system, which has been designed to work with uniprocessor and symmetrical multiprocessor (SMP)-based computers. To process input/output (I/O) requests, it uses packet-driven I/O, which utilizes I/O request packets (IRPs) and asynchronous I/O. Starting with Windows XP, Microsoft began making 64-bit versions of Windows available; before this, there were only 32-bit versions of these operating systems.
The Native API is a lightweight application programming interface (API) used by Windows NT and user mode applications. This API is used in the early stages of Windows NT startup process, when other components and APIs are still unavailable. Therefore, a few Windows components, such as the Client/Server Runtime Subsystem (CSRSS), are implemented using the Native API. The Native API is also used by subroutines such as those in kernel32.dll that implement the Windows API, the API based on which most of the Windows components are created.
The Microsoft Windows operating system supports a form of shared libraries known as "dynamic-link libraries", which are code libraries that can be used by multiple processes while only one copy is loaded into memory. This article provides an overview of the core libraries that are included with every modern Windows installation, on top of which most Windows applications are built.
The SemWare Editor (TSE) is a text editor computer program for MS-DOS, OS/2, Windows and Linux.
CWSDPMI is a 32-bit DPMI host written by Charles W. Sandmann from 1996 to 2010, currently at r7. It is loosely based upon prior GO32.EXE code used in DJGPP v1. It can provide DPMI 0.90+ 32-bit services for programs compiled with latest versions of DJGPP etc. compilers. Since r5, it can also be used for programs requiring a DPMI stub in lieu of PMODE/DJ. It supports up to 4 GB, virtual memory, and hardware interrupt reflection from real mode to protected mode. Programs compiled with DJGPP v2 require a DPMI host, which is usually CWSDPMI.EXE or CWSDPR0.EXE. In case of CWSDPMI.EXE, the default paging/virtual memory file is C:\CWSDPMI.SWP. It is capable of running on a 386 in under 512 KB of RAM.
The DOS API is an API which originated with 86-DOS and is used in MS-DOS/PC DOS and other DOS-compatible operating systems. Most calls to the DOS API are invoked using software interrupt 21h. By calling INT 21h with a subfunction number in the AH processor register and other parameters in other registers, various DOS services can be invoked. These include handling keyboard input, video output, disk file access, program execution, memory allocation, and various other activities. In the late 1980s, DOS extenders along with the DOS Protected Mode Interface (DPMI) allow the programs to run in either 16-bit or 32-bit protected mode and still have access to the DOS API.
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.
In computing on Microsoft platforms, WoW64 is a subsystem of the Windows operating system capable of running 32-bit applications on 64-bit Windows. It is included in all 64-bit versions of Windows—including Windows XP Professional x64 Edition, IA-64 and x64 versions of Windows Server 2003, as well as x64 versions of Windows Vista, Windows Server 2008, Windows 7, Windows 8, Windows Server 2012, Windows 8.1, Windows 10, Windows Server 2016, Windows Server 2019, Windows 11, Windows Server 2022, and Wine. as well as ARM64 versions of Windows 10, Windows 11 and Windows Server 2022, except in Windows Server Server Core where it is an optional component, and Windows Nano Server where it is not included. WoW64 aims to take care of many of the differences between 32-bit Windows and 64-bit Windows, particularly involving structural changes to Windows itself.
