Editing IBM TopView (section)

== History ==
When [[Microsoft]] announced [[Windows 1.0]] in November 1983, [[International Business Machines]] (IBM), Microsoft's important partner in popularizing MS-DOS for the [[IBM Personal Computer|IBM PC]], notably did not announce support for the forthcoming window environment.<ref name="MS Windows 1983">{{cite magazine |author-last=Markoff |author-first=John |title=Microsoft Does Windows |magazine=[[InfoWorld]] |volume=5 |issue=47 |pages=32–36 |publisher=[[CW Communications|Popular Computing, Inc.]] |location=Menlo Park, CA |date=1983-11-21 |url=https://books.google.com/books?id=uy8EAAAAMBAJ&pg=PA32 |issn=0199-6649}}</ref> IBM determined that the microcomputer market needed a [[computer multitasking|multitasking]] environment. When it released TopView in 1985, the press speculated that the software was the start of IBM's plan to increase its control over the IBM PC (even though IBM published the specifications publicly) by creating a proprietary operating system for it, similar to what IBM had offered for years on its larger computers.<ref name="edelhart19850430">{{cite magazine |url=https://books.google.com/books?id=vVNXxWE6BX0C&pg=PA125 |title=TopView Enters the Fray |magazine=[[PC Magazine]] |date=1985-04-30 |access-date=2013-10-28 |author-last=Edelhart |author-first=Mike |pages=125–126}}</ref> TopView also allowed IBM to serve customers who were surprised that the new [[IBM AT]] did not come with an [[operating system]] able to use the hardware multitasking and [[protected mode]] features of the new [[80286]] [[central processing unit|CPU]], as DOS and most applications were still running in 8086/8088 [[real mode]].

Even given TopView's virtual memory management capabilities, hardware limitations still held the new environment back&mdash;a base AT with 256 KB of RAM only had room for 80 KB of application code and data in RAM once DOS and TopView had loaded up.  512-640 KB was recommended to load up two typical application programs of the time. This was the maximum the earlier [[IBM Personal Computer XT|IBM XT]] could have installed. Once loaded, TopView took back much of the memory consumed by DOS, but still not enough to satisfy industry critics. TopView ran in real mode on any [[x86 architecture|x86]] processor and could run well behaved DOS programs (i.e. programs that did not write directly to the screen but used BIOS int 10h and DOS int 21h, such as the IBM Assistant Series of productivity programs) in an arrangement of windows.<ref name="prom">{{cite news |title=IBM TopView Promising but Has Limitations |date=1985-06-17 |author-first=Lawrence J. |author-last=Magid |url=https://www.latimes.com/archives/la-xpm-1985-06-17-fi-12704-story.html |work=[[Los Angeles Times]]}}</ref> Well behaved applications would use standard DOS and BIOS function calls to access system services and hardware. Misbehaving programs (i.e. such as programs that did write directly to the screen) such as Lotus 1-2-3, WordStar and dBase III would still run in the TopView environment, but would consume the entire screen.<ref name="IBM_1986_Announcement"/>  [[Object-oriented]] applications were written using the TopView API. TopView was developed to run on the 8088 (and required what IBM referred to as a fixed disk) and later the 80286. TopView was not updated to make use of the [[virtual 8086 mode]] added in the [[Intel 80386]] processors that allowed better [[Hardware-assisted virtualization|virtualization]].{{Citation needed|date=May 2011}}

Initially, compatibility with the extended features was limited mainly to IBM applications, along with a few third-party products like [[WordPerfect]] and [[VolksWriter]]. A chicken-and-egg situation developed where third-party developers were reluctant to add extended feature support (such as block insert and delete to allow users to do cut/copy/paste between applications) when they did not see market demand for them.<ref name="prom"/> Most DOS programs did, however, support these functions and did allow the user to perform the cut, copy, and paste operations by using the TopView pop-up menus.

Some believed that IBM planned to use TopView to force reliance on them to comply with the new technical specifications.<ref name="dvorak"/>  As later versions of TopView were released, it was able to successfully make more challenging DOS apps run in a multitasking fashion by intercepting direct access to system services and hardware.

TopView first introduced [[Program Information File]]s (PIF files), which defined how a given DOS program should be run in a multi-tasking environment, notably to avoid giving it unnecessary resources which could remain available to other programs. TopView's PIF files were inherited and extended by [[Quarterdeck Office Systems|Quarterdeck]]'s [[DESQview]] and [[Microsoft Windows]].<ref>{{cite journal |url=https://drdobbs.com/architecture-and-design/undocumented-corner/184409042 |magazine=[[Dr. Dobb's Journal]] |department=Undocumented Corner |title=The PIF File Format, or, TopView (sort of) Lives! |date=July 1, 1993}}</ref> The concept of Program Information Files was also used under [[Digital Research]] operating systems such as [[Concurrent DOS]]<!-- at least in Concurrent DOS XM and Concurrent DOS 386 since 1987 -->, [[Multiuser DOS]], [[Datapac System Manager]] and [[REAL/32]]; however, using the PIFED command, the necessary program information got directly embedded into the .EXE or .COM executable file.<ref>{{cite book |publisher=[[Digital Research]] |title=Concurrent DOS 386 - Multiuser/Multitasking Operating System - Reference Manual'' |date=1987 |url=http://bitsavers.trailing-edge.com/pdf/digitalResearch/concurrent/1126-2064-001_Concurrent_DOS_386_Reference_Guide_Nov87.pdf}}</ref>