|This is an old revision of this page, as edited by Josh the Nerd at 03:34, 29 April 2007 (EMS support has nothing to do with HMA). The present address (URL) is a permanent link to this revision, which may differ significantly from the .|
Windows 2.0 was the first version to support free-moving overlapping windows
|OS family||Microsoft Windows|
|Source model||Closed source|
|Released to |
|November 1 1987|
|Latest release||2.11 / March 13 1989|
|Official website||Windows Desktop Products History|
|Unsupported as of December 31 2001|
Windows 2.x is a family of Microsoft Windows graphical user interface-based operating environments that superseded Windows 1.0. Windows 2.x was said to look similar to the original Mac OS and more closely matched Microsoft's pre-release publicity for Windows 1.0.
Released on November 23 1987, Windows 2.0 allows for windows to overlap each other, in contrast to Windows 1.0, which can only display tiled windows (this limitation was imposed due to lawsuits from Apple Computer although some argue that the dialog boxes and drop-down menus in Windows 1.0 are overlapping windows). This version also introduced the window-manipulation terminology of "Minimize" and "Maximize", as opposed to "Iconize" and "Zoom" in Windows 1.0, and a more sophisticated keyboard-shortcut mechanism in which shortcut keys are identified by underlining the character that, in conjunction with the "Alt" key, causes them to be selected.
The first Windows versions of Microsoft Word and Microsoft Excel run on Windows 2.0. Third-party developer support for Windows increased substantially with this version (some shipping the Windows Runtime software with their applications, for customers who had not purchased the full version of Windows). However, most developers still maintained DOS versions of their applications, as Windows users were still a distinct minority of their market.
Windows 2.03, which features some Mac-like icons, was released in January of 1988. On March 17 1988, Apple filed suit against Microsoft and Hewlett Packard, accusing them of violating copyrights Apple held on the Macintosh System Software.
Less than a year later, Windows/286 2.1 and Windows/386 2.1 were released on May 27 1988. These versions can take advantage of the specific features of the Intel 80286 and Intel 80386 processors. In March 1989, Windows 2.11 was released, with some minor changes in memory management, faster printing and postscript drivers.
Windows/286 takes advantage of the HMA to increase the memory available to Windows programs. It introduced the himem.sys DOS driver for this purpose. It also includes support for several EMS boards (this support is not related to the 80286 processor per-se). The segmented nature of Windows programs is quite suited to the usage of EMS, as portions of code and data can be made visible in the first megabyte of memory accessible to real-mode programs only when the program using them is given control. Microsoft encouraged users to configure their computers with only 256KB of main memory, leaving the address space from 256-640KB available for dynamic mapping of EMS memory.
Windows/386 is much more advanced. It introduced a protected mode kernel, above which the GUI and applications run as a virtual 8086 mode task. It allows several MS-DOS programs to run in parallel in virtual machines, rather than always suspending background applications. (Windows applications could already run in parallel through cooperative multitasking.) Each DOS application can use as much low memory as is available before Windows is started, minus a few kilobytes of overhead. Windows/386 also provides EMS emulation, using the memory management features of the 80386 to make RAM beyond 640K behave like the banked memory previously only supplied by add-in cards and used by popular DOS applications. (By overwriting the WIN200.BIN file with COMMAND.COM, it is possible to use the EMS emulation in DOS without starting the Windows GUI.) There is no disk-based virtual memory, so multiple DOS programs have to fit inside the available physical memory; Microsoft suggested buying additional memory (and cards) if necessary.
Neither of these versions work with DOS memory managers like CEMM or QEMM or with DOS extenders, which have their own extended memory management and run in protected mode as well. This was remedied in version 3.0, which is compatible with VCPI in "standard mode" and with DPMI in "386 enhanced" mode. Windows 3.0 also has the capability of using the DWEMM Direct Write Enhanced Memory Module. This is what enables the far faster and sleek graphical user interface.
The various Windows 2.x versions were superseded by Windows 3.0 in May 1990.
-  - Microsoft article with details about the different versions of Windows
Footnotes and references
- "1980 - 1989: An Industrial Milestone". The Apple Museum. Retrieved 2006-06-25.
- On 286-based PCs, EMS memory can be made available by adding hardware EMS memory expansion cards. This is different from the later emulation of EMS memory via EMM386, which requires a 386 processor. These EMS boards were however not very common.