MS-DOS API

The MS-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 (INT 21h). By calling INT 21h with a subfunction number in the AH processor register and other parameters in other registers, one invokes various DOS services. DOS services include keyboard input, video output, disk file access, executing programs, memory allocation, and various other things. 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.

History of the DOS API

The original DOS API in 86-DOS and MS-DOS 1.0 was designed to be functionally compatible with CP/M. Files were accessed using file control blocks (FCBs). The DOS API was greatly extended in MS-DOS 2.0 with several Unix concepts, including file access using file handles, hierarchical directories and device I/O control. In DOS 3.1, network redirector support was added. In MS-DOS 3.31, the INT 25h/26h functions were enhanced to support hard disks greater than 32 MB. MS-DOS 5 added support for using upper memory blocks (UMBs). After MS-DOS 5, the DOS API was unchanged for the successive standalone releases of DOS.

MS-DOS

MS-DOS (/ˌɛmɛsˈdɒs/ EM-es-DOSS; acronym for Microsoft Disk Operating System) is an operating system for x86-based personal computers mostly developed by Microsoft. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid-1990s, when it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system by Microsoft Corporation.

MS-DOS resulted from a request in 1981 by IBM for an operating system to use in its IBM PC range of personal computers. Microsoft quickly bought the rights to 86-DOS from Seattle Computer Products, and began work on modifying it to meet IBM's specification. IBM licensed and released it in August 1981 as PC DOS 1.0 for use in their PCs. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, in subsequent years the two products diverged and became different from each other, with recognizable differences in compatibility, syntax, and capabilities.

MS-DOS 4.0 (multitasking)

MS-DOS 4.0 was a multitasking release of MS-DOS developed by Microsoft based on MS-DOS 3.1. Lack of interest from OEMs, particularly IBM, led to it being released only in a scaled-back form. It is sometimes referred to as European MS-DOS 4.0, as it was primarily used there. It should not be confused with PC DOS 4.00 or MS-DOS 4.01 and later, which did not contain the multi-tasking features.

History

Apricot Computers pre-announced "MS-DOS 4.0" in early 1986, and Microsoft demonstrated it in September of that year at a Paris trade show. However, only a few European OEMs, such as SMT Goupil and International Computers Limited (ICL), actually licensed releases of the software. In particular, IBM declined the product, concentrating instead on improvements to MS-DOS 3.x and their new joint development with Microsoft to produce OS/2.

As a result, the project was scaled back, and only those features promised to particular OEMs were delivered. In September 1987, a version of multi-tasking MS-DOS 4.1 was reported to be developed for the ICL DRS Professional Workstation (PWS). No further releases were made once the contracts had been fulfilled.

Windows ME

Windows Millennium Edition, or Windows ME (marketed with the pronunciation of the pronoun "me", but commonly pronounced as an initialism, "M-E"), is a graphical operating system from Microsoft released to manufacturing in June 2000, and launched in September 2000. It was the last operating system released in the Windows 9x series.

Windows ME was the successor to Windows 98 SE and was targeted specifically at home PC users. It included Internet Explorer 5.5, Windows Media Player 7, and the new Windows Movie Maker software, which provided basic video editing and was designed to be easy to use for home users. Microsoft also updated the graphical user interface, shell features, and Windows Explorer in Windows ME with some of those first introduced in Windows 2000, which had been released as a business-oriented operating system seven months earlier. Windows ME could be upgraded to Internet Explorer 6 SP1 (but not to SP2 (SV1) or Internet Explorer 7), Outlook Express 6 SP1 and Windows Media Player 9 Series. Microsoft .NET Framework up to and including version 2.0 is supported; however, versions 2.0 SP1, 3.x, and greater are not. Office XP was the last version of Microsoft Office to be compatible with Windows ME.