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History
Main article: History of operating systems
In the beginning
Proprietary operating systems were made to sell the company’s hardware. Without system software (compilers and operating systems), a budding hardware developer had great difficulty launching a computer; the availability of operating systems not tied to a single hardware supplier - such as Digital Research’s CP/M for microcomputers, and Unix for larger computers - greatly transformed the computer industry; someone with an innovative idea could easily start producing hardware on which buyers could use standard software. In 1969-70, UNIX first appeared on the PDP-7 and later the PDP-11. It soon became capable of providing cross-platform time sharing using preemptive multitasking, advanced memory management, memory protection, and a host of other advanced features. UNIX soon gained popularity as an operating system for mainframes and minicomputers alike. Unix was inspired by Multics, as were several other operating systems, such as Data General’s AOS-VS, and IBM’s addition of such concepts as subdirectories to PC DOS in version 2.0.
Microsoft bought QDOS from Seattle Computer Products, a very simple diskette operating system somewhat similar to CP/M, to create an operating system, PC DOS, for the launch of the IBM PC, under a deal with IBM where Microsoft could still sell the operating system as MS DOS for non-IBM computers. Microsoft produced odd-numbered major version numbers while IBM was responsible for even revision numbers (2.0, 2.1, 4.0, etc) of the code base until version 6. There was very little difference between MS-DOS and PC-DOS, one example being the inclusion of GW-BASIC with MS-DOS (because some BASIC code in IBM PC ROMs was not legally allowed to be put into non-IBM computers). MS-DOS and PC-DOS soon became known simply as “DOS” (the term is now usually taken to also include other “DOSes” such as DR-DOS and FreeDOS, but it should not be confused with the command prompt program within some operating systems, COMMAND.COM). Although MS-DOS could be tailored to hardware significantly different to IBM’s PC, it soon became common for hardware vendors to make their equipment as compatible as possible with the IBM PC and its immediate IBM successors (the PC-XT and later IBM PC-AT models), since many popular DOS programs bypassed the operating system to access hardware directly for speed, requiring other manufactures to closely copy the IBM design, including its limitations. The availability of MS-DOS had two major effects on the computer industry: the commercial acceptability of “sneaky tricks” (as documented, for example, in Ralf Brown’s Interrupt List) to gain speed or functionality or copy-protection, and a market that demanded extreme compatibility (speed and cosmetic differences were the only acceptable innovations) , solar panel used .
IBM PC compatibles could also run Microsoft Xenix, a UNIX-like operating system from the early 1980s. Xenix was heavily marketed by Microsoft as a multi-user alternative to its single user MS-DOS operating system. The CPUs of these personal computers could not facilitate kernel memory protection or provide dual mode operation, so Xenix relied on cooperative multitasking and had no protected memory , lcd used .
The 80286-based IBM PC AT was the first IBM compatible personal computer capable of providing protected memory mode operation. However, this mode was hampered by software bugs in its implementation on the 286, and not widely accepted until the release of the Intel 80386. With the 386 porting BSD Unix to a PC became feasible, and various Unix-like systems (tagged “*nix” at the time), including Linux, arose, but IBM (and, initially, Microsoft) opted for OS/2 from the inception of the PS/2; Microsoft eventually going its own way with Microsoft Windows firstly as a GUI on top of DOS, then as a complete operating system.
Classic Mac OS, and Microsoft Windows 1.0-3.11 supported only cooperative multitasking (Windows 95, 98, & ME supported preemptive multitasking only when running 32-bit applications, but ran legacy 16-bit applications using cooperative multitasking), and were very limited in their abilities to take advantage of protected memory. Application programs running on these operating systems must yield CPU time to the scheduler when they are not using it, either by default, or by calling a function.
Windows NT’s underlying operating system kernel which was designed by essentially the same team as Digital Equipment Corporation’s VMS, a UNIX-like operating system which provided protected mode operation for all user programs, kernel memory protection, preemptive multi-tasking, virtual file system support, and a host of other features.
Classic AmigaOS and versions of Microsoft Windows from Windows 1.0 through Windows Me did not properly track resources allocated by processes at runtime.[citation needed] If a process had to be terminated, the resources might not be freed up for new programs until the machine was restarted.
The AmigaOS did have preemptive multitasking, as did operating systems for many larger (“supermini”) computers that, despite being technically better, were struggling in sales when faced with the mass production of increasingly-faster “Personal” Computers and customers locked into non-portable software (legacy software and proprietary office documents).
Mainframes
Through the 1950s, many major features were pioneered in the field of operating systems. The development of the IBM System/360 produced a family of mainframe computers available in widely differing capacities and price points, for which a single operating system OS/360 was planned (rather than developing ad-hoc programs for every individual model). This concept of a single OS spanning an entire product line was crucial for the success of System/360 and, in fact, IBM`s current mainframe operating systems are distant descendants of this original system; applications written for the OS/360 can still be run on modern machines. In the mid-70’s, the MVS, the descendant of OS/360 offered the first[citation needed] implementation of using RAM as a transparent cache for disk resident data.
OS/360 also pioneered a number of concepts that, in some cases, are still not seen outside of the mainframe arena. For instance, in OS/360, when a program is started, the operating system keeps track of all of the system resources that are used including storage, locks, data files, and so on. When the process is terminated for any reason, all of these resources are re-claimed by the operating system. An alternative CP-67 system started a whole line of operating systems focused on the concept of virtual machines.
Control Data Corporation developed the SCOPE operating system in the 1960s, for batch processing. In cooperation with the University of Minnesota, the KRONOS and later the NOS operating systems were developed during the 1970s, which supported simultaneous batch and timesharing use. Like many commercial timesharing systems, its interface was an extension of the Dartmouth BASIC operating systems, one of the pioneering efforts in timesharing and programming languages. In the late 1970s, Control Data and the University of Illinois developed the PLATO operating system, which used plasma panel displays and long-distance time sharing networks. Plato was remarkably innovative for its time, featuring real-time chat, and multi-user graphical games. Burroughs Corporation introduced the B5000 in 1961 with the MCP, (Master Control Program) operating system. The B5000 was a stack machine designed to exclusively support high-level languages with no machine language or assembler, and indeed the MCP was the first OS to be written exclusively in a high-level language ESPOL, a dialect of ALGOL. MCP also introduced many other ground-breaking innovations, such as being the first commercial implementation of virtual memory. During development of the AS400, IBM made an approach to Burroughs to licence MCP to run on the AS400 hardware. This proposal was declined by Burroughs management to protect its existing hardware production. MCP is still in use today in the Unisys ClearPath/MCP line of computers.
UNIVAC, the first commercial computer manufacturer, produced a series of EXEC operating systems. Like all early main-frame systems, this was a batch-oriented system that managed magnetic drums, disks, card readers and line printers. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the Dartmouth BASIC system.
General Electric and MIT developed General Electric Comprehensive Operating Supervisor (GECOS), which introduced the concept of ringed security privilege levels. After acquisition by Honeywell it was renamed to General Comprehensive Operating System (GCOS).
Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Prior to the widespread use of UNIX, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community.
In the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported software to run on more than one system. Early systems had utilized microprogramming to implement features on their systems in order to permit different underlying architecture to appear to be the same as others in a series. In fact most 360’s after the 360/40 (except the 360/165 and 360/168) were microprogrammed implementations. But soon other means of achieving application compatibility were proven to be more significant.
The enormous investment in software for these systems made…
