In computing, time-sharing is the concurrent sharing of a computing resource among many tasks or users by giving each task or user a small slice of processing time. This quick switch between tasks or users gives the illusion of simultaneous execution. It enables multi-tasking by a single user or enables multiple-user sessions.
In computing, a virtual machine (VM) is the virtualization or emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination of the two. Virtual machines differ and are organized by their function, shown here:
In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very large (main) memory".
The Conversational Monitor System is a simple interactive single-user operating system. CMS was originally developed as part of IBM's CP/CMS operating system, which went into production use in 1967. CMS is part of IBM's VM family, which runs on IBM mainframe computers. VM was first announced in 1972, and is still in use today as z/VM.
This article presents a timeline of events in the history of computer operating systems from 1951 to the current day. For a narrative explaining the overall developments, see the History of operating systems.
The Compatible Time-Sharing System (CTSS) was the first general purpose time-sharing operating system. Compatible Time Sharing referred to time sharing which was compatible with batch processing; it could offer both time sharing and batch processing concurrently.
VM is a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers.
CP/CMS is a discontinued time-sharing operating system of the late 1960s and early 1970s. It is known for its excellent performance and advanced features. Among its three versions, CP-40/CMS was an important 'one-off' research system that established the CP/CMS virtual machine architecture. It was followed by CP-67/CMS, a reimplementation of CP-40/CMS for the IBM System/360-67, and the primary focus of this article. Finally, CP-370/CMS was a reimplementation of CP-67/CMS for the System/370. While it was never released as such, it became the foundation of IBM's VM/370 operating system, announced in 1972.
A hypervisor, also known as a virtual machine monitor (VMM) or virtualizer, is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called a host machine, and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems. Unlike an emulator, the guest executes most instructions on the native hardware. Multiple instances of a variety of operating systems may share the virtualized hardware resources: for example, Linux, Windows, and macOS instances can all run on a single physical x86 machine. This contrasts with operating-system–level virtualization, where all instances must share a single kernel, though the guest operating systems can differ in user space, such as different Linux distributions with the same kernel.
SCRIPT, any of a series of text markup languages starting with Script under Control Program-67/Cambridge Monitor System (CP-67/CMS) and Script/370 under Virtual Machine Facility/370 (VM/370) and the Time Sharing Option (TSO) of OS/VS2; the current version, SCRIPT/VS, is part of IBM's Document Composition Facility (DCF) for IBM z/VM and z/OS systems. SCRIPT was developed for CP-67/CMS by Stuart Madnick at MIT, succeeding CTSS RUNOFF.
VP/CSS was a time-sharing operating system developed by National CSS. It began life in 1968 as a copy of IBM's CP/CMS, which at the time was distributed to IBM customers at no charge, in source code form, without support, as part of the IBM Type-III Library. Through extensive in-house development, in what today would be termed a software fork, National CSS took VP/CSS in a different direction from CP/CMS. Although the two systems would eventually share many capabilities, their technical implementations diverged in substantive ways.
In computing, virtualization is the use of a computer to simulate another computer. The following is a chronological list of virtualization technologies.
The IBM Cambridge Scientific Center was a company research laboratory established in February 1964 in Cambridge, Massachusetts. Situated at 545 Technology Square, in the same building as MIT's Project MAC, it was later renamed the IBM Scientific Center. It is most notable for creating the CP-40 and the control program portions of CP/CMS, a virtual machine operating system developed for the IBM System/360-67.
CP-40 was a research precursor to CP-67, which in turn was part of IBM's then-revolutionary CP[-67]/CMS – a virtual machine/virtual memory time-sharing operating system for the IBM System/360 Model 67, and the parent of IBM's VM family. CP-40 ran multiple instances of client operating systems – particularly CMS, the Cambridge Monitor System, built as part of the same effort. Like CP-67, CP-40 and the first version of CMS were developed by IBM's Cambridge Scientific Center (CSC) staff, working closely with MIT researchers at Project MAC and Lincoln Laboratory. CP-40/CMS production use began in January 1967. CP-40 ran on a unique, specially modified IBM System/360 Model 40.
The IBM System/360 Model 67 (S/360-67) was an important IBM mainframe model in the late 1960s. Unlike the rest of the S/360 series, it included features to facilitate time-sharing applications, notably a Dynamic Address Translation unit, the "DAT box", to support virtual memory, 32-bit addressing and the 2846 Channel Controller to allow sharing channels between processors. The S/360-67 was otherwise compatible with the rest of the S/360 series.
This article covers the History of CP/CMS — the historical context in which the IBM time-sharing virtual machine operating system was built.
The IBM M44/44X was an experimental computer system from the mid-1960s, designed and operated at IBM's Thomas J. Watson Research Center at Yorktown Heights, New York. It was based on a modified IBM 7044, and simulated multiple 7044 virtual machines, using both hardware and software. Key team members were Dave Sayre and Rob Nelson. This was a groundbreaking machine, used to explore paging, the virtual machine concept, and computer performance measurement. It was purely a research system, and was cited in 1981 by Peter Denning as an outstanding example of experimental computer science.
The history of IBM mainframe operating systems is significant within the history of mainframe operating systems, because of IBM's long-standing position as the world's largest hardware supplier of mainframe computers. IBM mainframes run operating systems supplied by IBM and by third parties.
Robert Jay Creasy was the project leader of the first full virtualization hypervisor, the IBM CP-40, which later developed into IBM's highly successful line of mainframe VM operating systems.
Edson C. Hendricks, an IBM computer scientist, developed RSCS, fundamental software that powered the world’s largest network prior to the Internet and which directly influenced both Internet development and user acceptance of networking between independently managed organizations. Within IBM, the resulting network later became known as VNET and grew to 4000 nodes. In the academic community, VNET formed the base for BITNET which extended to 500 organizations and 3,000 nodes. VNET was also the networking design underpinning EARN in Europe, and NETNORTH in Canada.
