timesharingtime sharingtime-sharing system
DEC TSS-8 → RSTS-11, RSX-11 → VAX/VMS. English Electric KDF9 COTAN (Culham Online Task Activation Network). HP 2000 Time-Shared BASIC. HP 3000 series. IBM CALL/360, CALL/OS - using IBM System/360 Model 50. IBM CP-40 → CP-67 → CP-370 → CP/CMS → VM/CMS. IBM TSO for OS/MVT → for OS/VS2 → for MVS → for z/OS. IBM TSS/360 → TSS/370. ICT 1900 series GEORGE 3 MOP (Multiple Online Programming). International Timesharing Corporation on dual CDC 3300 systems. MIT CTSS → MULTICS (MIT / GE / Bell Labs) → Unix. MIT Time-sharing System for the DEC PDP-1 → ITS. McGill University MUSIC → IBM MUSIC/SP. Michigan Terminal System, on the IBM S/360-67, S/370, and successors.

Parallels Workstation

Linux or MAC OS X virtualizationParallels
The hypervisor directly controls some of the host machine's hardware resources and provides an interface to it for both virtual machine monitors and primary OS. This allows virtualization software to reduce overhead. Parallels Workstation's hypervisor also supports hardware virtualization technologies like Intel VT-x and AMD-V. Parallels Workstation is a hardware emulation virtualization software, in which a virtual machine engine enables each virtual machine to work with its own processor, RAM, floppy drive, CD drive, I/O devices, and hard disk – everything a physical computer contains.

VMware Workstation

Ready-made Linux VMs set up for different purposes are available from several sources. VMware Workstation supports bridging existing host network adapters and sharing physical disk drives and USB devices with a virtual machine. It can simulate disk drives; an ISO image file can be mounted as a virtual optical disc drive, and virtual hard disk drives are implemented as .vmdk files. VMware Workstation Pro can save the state of a virtual machine (a "snapshot") at any instant. These snapshots can later be restored, effectively returning the virtual machine to the saved state, as it was and free from any post-snapshot damage to the VM.


Oracle VirtualBoxVDIPortable-VirtualBox
Virtual machine groups — allows management of a group of virtual machines as a single unit (power them on or off, take snapshots, etc.). Some VM settings can be altered during VM execution. Support up to 36 NICs in case of the ICH9 chipset. Support for limiting network I/O bandwidth. Can automatically run VMs on host system startup (except on Windows hosts). Since version 4.3. VM video-capture support. Host touch device support (GUI passes host touch events to guest)/USB virtualization of such devices. Since version 5.0. Paravirtualization support for Windows and Linux guests to improve time-keeping accuracy and performance. USB3 controller based on Intel's hardware implementation.

Adaptive Domain Environment for Operating Systems

The first is simulation-based and provides a virtual environment for which to run additional operating systems. The second suggests the usage of a nanokernel layer to enable hardware sharing. In the simulation category there are tools such as VMware, Plex86, VirtualPC and SimOS. There is also KVM which is more similar to Adeos but is not RT and requires specific virtualization hardware support. These solutions are used for users who desire to run applications foreign to their base OS, they provide no control whatsoever over the base OS to the user. Simulation was never meant to be used in a production environment.


Win4Lin ProNeTraverseVirtual Bridges
Citing changes in the desktop virtualization industry, the software's publisher, Virtual Bridges, has discontinued Win4Lin Pro. In 2006, Win4Lin came in three different versions, depending on the virtualization requirements of the user. Win4Lin Pro used "full" virtualization, whereas Win4Lin 9x was an example of paravirtualization. The Win4Lin 9x/Pro (henceforth the only technology discussed in this section) operates by running Windows applications in a virtual machine.

English language

The modern English alphabet contains 26 letters of the Latin script: a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z (which also have capital forms: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z). The spelling system, or orthography, of English is multi-layered, with elements of French, Latin, and Greek spelling on top of the native Germanic system. Further complications have arisen through sound changes with which the orthography has not kept pace.

VMware Server

vCenter Server Appliance
(Microsoft Virtual Server 2005 R2 SP1 also supports Shadow Copy.) Virtual machines that support this service can be backed up without stopping. VMware Server was discontinued in January 2010; general support ended on June 30, 2011. * VMware Server End-User License Virtual appliance. Virtual machine. Platform virtualization. x86 virtualization. Virtual disk image.

Parallels Desktop for Mac

Parallels DesktopParallelsCoherence (software)
Desktop virtualization. Virtual machine. Platform virtualization. x86 virtualization. Virtual disk image.


Virtual MachineVMzVM
z/VM is the current version in IBM's VM family of virtual machine operating systems. z/VM was first released in October 2000 and remains in active use and development. It is directly based on technology and concepts dating back to the 1960s, with IBM's CP/CMS on the IBM System/360-67 (see article History of CP/CMS for historical details). z/VM runs on IBM's IBM Z family of computers. It can be used to support large numbers (thousands) of Linux virtual machines. (See Linux on IBM Z.) On October 16, 2018, IBM released z/VM Version 7.1 which requires z/Architecture, implemented in IBM's EC12, BC12 and later models. * IBM z/VM Evaluation Edition (free download) z/OS.

Computing platform

platformplatformssoftware platform
A virtual machine (VM) such as the Java virtual machine or .NET CLR. Applications are compiled into a format similar to machine code, known as bytecode, which is then executed by the VM. A virtualized version of a complete system, including virtualized hardware, OS, software, and storage. These allow, for instance, a typical Windows program to run on what is physically a Mac. AmigaOS, AmigaOS 4. FreeBSD, NetBSD, OpenBSD. IBM i. Linux. Microsoft Windows. OpenVMS. Classic Mac OS. macOS. OS/2. Solaris. Tru64 UNIX. VM. QNX. z/OS. Android. Bada. BlackBerry OS. Firefox OS. iOS. Embedded Linux. Palm OS. Symbian. Tizen. WebOS. LuneOS. Windows Mobile. Windows Phone.

IBM mainframe

IBM mainframesmainframeIBM mainframe computers
The virtual memory capabilities also allowed the system to support virtual machines; the VM/370 hypervisor would run one or more virtual machines running either standard System/360 or System/370 operating systems or the single-user Conversational Monitor System (CMS). A time-sharing VM system could run multiple virtual machines, one per user, with each virtual machine running an instance of CMS. The zSeries family, introduced in 2000 with the z900, included IBM's newly designed 64-bit z/Architecture.


The chief difference from CP-40 was that SIMMON supported a single virtual machine for testing of a single guest program running there. CP-40 supported many virtual machines for time-sharing production work. CP-40 evolved by many stages into the present VM/CMS operating system. SIMMON was a useful test vehicle for many years. SIMMON was designed to dynamically include independently developed programs (test tools) for testing the target guest program. The SIMMON kernel maintained control over the hardware (and the guest) and coordinated invocation of the test tools.


zSeriesIBM System zSystem z
First layer virtualization is provided by the Processor Resource and System Manager (PR/SM) to deploy one or more Logical Partitions (LPARs). Each LPAR supports a variety of operating systems. A hypervisor called z/VM can also be run as the second layer virtualization in LPARs to create as many virtual machines (VMs) as there are resources assigned to the LPARs to support them. The first layer of IBM Z virtualization (PR/SM) allows a z machine to run a limited number of LPARs (up to 80 on the IBM z13).

Virtual Machine Communication Facility

The IBM Virtual Machine Communication Facility (VMCF) is a feature of the VM/370 operating system introduced in Release 3 in 1976. It "provides a method of communication and data transfer between virtual machines operating under the same VM/370 system." VMCF uses paravirtualization through the diagnose instruction VMCF function to send data, in blocks of up to 2048 bytes, from one virtual machine to another. The receiving virtual machine accesses the data thru the diagnose function. It provides a simpler interface and greater performance than the prior use of virtual channel-to-channel adapters for the same purpose. * Inter User Communication Vehicle

Assembly language

assemblerassemblyassembly code
This was done, for example, by systems programmers working with IBM's Conversational Monitor System / Virtual Machine (VM/CMS) and with IBM's "real time transaction processing" add-ons, Customer Information Control System CICS, and ACP/TPF, the airline/financial system that began in the 1970s and still runs many large computer reservation systems (CRS) and credit card systems today.

Time-sharing system evolution

., OS/2 was more influenced by VAX/VMS than by MS-DOS, but its legacy is as an x86 platform). The Cambridge Multiple-Access System was the first time-sharing system developed outside the United States. History of CP/CMS has many period details and sources. Timeline of operating systems.

VMware ESXi

VMware ESXESXiVMware ESX Server
Paravirtualization or other virtualization techniques may help with these issues. VMware developed the Virtual Machine Interface for this purpose, and selected operating systems support this. A comparison between full virtualization and paravirtualization for the ESX Server shows that in some cases paravirtualization is much faster.

Virtual Iron

Additional features included disk and virtual machine cloning (snapshots), IPMI/ILO support, etc. Virtual Iron had implemented full virtualization (requiring hardware-assisted virtualization which it called native virtualization) over paravirtualization. Native virtualization allowed for unmodified guest operating systems and had the advantage of hardware advances for better performance. Virtual Iron, Inc claimed to have pioneered the implementation of native virtualization. Virtual Iron discussed paravirtualization and native virtualization in its blog: Virtual Iron has decided against paravirtualization in favor of "native virtualization."


GNU/LinuxLinux on the desktopLin
A number of Java Virtual Machines and development kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM's J2SE RE, as well as many open-source projects like Kaffe and JikesRVM. GNOME and KDE are popular desktop environments and provide a framework for developing applications. These projects are based on the GTK+ and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages.

Bare machine

bare metalbare-metalbare hardware machine
In computer science, bare machine (or bare metal) refers to a computer executing instructions directly on logic hardware without an intervening operating system. Modern operating systems evolved through various stages, from elementary to the present day complex, highly sensitive systems incorporating many services. After the development of programmable computers (which did not require physical changes to run different programs) but prior to the development of operating systems, sequential instructions were executed on the computer hardware directly using machine language without any system software layer. This approach is termed the "bare machine" precursor to modern operating systems.


International Business MachinesIBM CorporationInternational Business Machines Corporation
Famous inventions and developments by IBM include: the Automated teller machine (ATM), Dynamic random access memory (DRAM), the electronic keypunch, the financial swap, the floppy disk, the hard disk drive, the magnetic stripe card, the relational database, RISC, the SABRE airline reservation system, SQL, the Universal Product Code (UPC) bar code, and the virtual machine. Additionally, in 1990 company scientists used a scanning tunneling microscope to arrange 35 individual xenon atoms to spell out the company acronym, marking the first structure assembled one atom at a time. A major part of IBM research is the generation of patents.


voice mailvoice-mailvoice messaging
Other interesting markets developed from the carrier market including a concept called "virtual telephony". Virtual Telephony, developed by Octel, used voicemail to provide phone service rapidly in emerging countries without wiring for telephones. The problem this solved was that emerging countries did not have many telephones. Wiring for telephones was very expensive, and many poorer citizens didn't have homes to wire. The economies of emerging countries were held back partly because people could not communicate beyond the area where they could walk or ride a bicycle. Giving them phones was one way to help their economies, but there was not a practical way to do it.

X86 virtualization

Intel VT-xAMD-VVT-x
Later, it was branded as APIC virtualization (APICv) and it became commercially available in the Ivy Bridge EP series of Intel CPUs, which is sold as Xeon E5-26xx v2 (launched in late 2013) and as Xeon E5-46xx v2 (launched in early 2014). Graphics Virtualization Technology was introduced with Intel Iris Pro. Intel's integrated GPU can be either dedicatedly assigned to a virtual machine (GVT-d), shared between multiple virtual machines on a time-sharing basis while using native graphics driver (GVT-g), or shared between multiple virtual machines by using a virtual graphics driver (GVT-s). Memory and I/O virtualization is performed by the chipset.


Hyperjacking is an attack in which a hacker takes malicious control over the hypervisor that creates the virtual environment within a virtual machine (VM) host. The point of the attack is to target the operating system that is below that of the virtual machines so that the attacker's program can run and the applications on the VMs above it will be completely oblivious to its presence. Hyperjacking involves installing a malicious, fake hypervisor that can manage the entire server system. Regular security measures are ineffective because the operating system will not be aware that the machine has been compromised.