# VM

> family of IBM virtual machine operating systems

**Wikidata**: [Q5013572](https://www.wikidata.org/wiki/Q5013572)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/VM_(operating_system))  
**Source**: https://4ort.xyz/entity/vm

## Summary
VM is a family of IBM virtual-machine operating systems that lets many complete systems run at once on the same mainframe. Originally released in the early 1970s as VM/370, it evolved into today’s z/VM and remains IBM’s flagship hypervisor for z/Architecture hardware.

## Key Facts
- Developed by IBM; first shipped as VM/370 for System/370 in 1972.
- Written in IBM assembly language and operates as a true hypervisor, hosting multiple independent “virtual machines.”
- Runs on IBM System/360, System/370, S/390, and current z/Architecture processors.
- Current generation is branded z/VM; earlier names include VM/CMS, VM/370, CP-370.
- Native file system is the CMS file system; also supports IBM PROFS, MAGMA-Lisp, and IBM Cross System Product workloads.
- Supports up to hundreds of concurrent virtual machines on a single physical processor.
- Described in Wikidata as both an operating system and a hypervisor; 9 Wikipedia language editions cover the topic.
- Official product page: http://www.vm.ibm.com/

## FAQs
### Q: What does VM actually stand for?
A: VM is not an acronym; IBM uses it to mean “Virtual Machine,” referring to the system’s ability to create multiple isolated virtual mainframes on one physical box.

### Q: Is VM still sold today?
A: Yes—IBM continues to develop and license the line under the name z/VM for its z/Architecture mainframes, with the latest releases supporting 64-bit guests and thousands of virtual servers.

### Q: How is VM different from z/OS?
A: z/OS is a single traditional operating system, whereas VM is a hypervisor that can run many copies of z/OS, Linux, or older systems side-by-side without interference.

### Q: Can I run open-source software on VM?
A: Absolutely—z/VM is widely used to host hundreds or thousands of virtual Linux instances on one mainframe, consolidating workloads while preserving isolation.

## Why It Matters
Before VMware or Xen existed, IBM’s VM family proved that full hardware virtualization was commercially practical. By letting customers spin up entire mainframes in software, VM eliminated the need to buy separate physical boxes for development, testing, and production. This capability drove massive cost savings and higher hardware utilization in data centers that could afford a single large IBM system. Over five decades the product line has evolved from VM/370 on 24-bit hardware to today’s 64-bit z/VM, yet the core idea—run many complete systems on one processor—remains unchanged. Modern banks, airlines, and governments still rely on z/VM to host thousands of Linux guests alongside legacy z/OS and VSE workloads, making it a quiet but critical piece of global IT infrastructure.

## Notable For
- First commercially successful mainframe hypervisor, shipping years before the term “hypervisor” was common.
- Enabled IBM mainframes to achieve >90 % CPU utilization by consolidating test, staging, and production on one machine.
- Still supports binary compatibility for 1970s System/370 guests under today’s z/VM releases.
- Powers some of the world’s largest virtual-server farms, with single systems running over 10 000 Linux guests.

## Body
### Origins and Architecture
IBM announced VM/370 in August 1972 as a re-implementation of earlier research done for System/360 Model 67. The Control Program (CP) creates virtual machines that each look like a complete System/370, including virtual CPUs, memory, and I/O devices. Users log into a Conversational Monitor System (CMS) session that acts as an interactive single-user operating system inside its own VM.

### Evolution of Names and Releases
- 1972 – VM/370 Release 1
- 1980s – VM/SP, VM/XA, VM/ESA add extended architecture and XA-64 support
- 2000 – Re-branded z/VM for 64-bit z/Architecture
- Current releases (z/VM 7.x) support secure guests, virtual SMP, and live relocation

### Software Ecosystem
Beyond CMS, IBM offered PROFS (office automation), MAGMA-Lisp for AI research, and Cross System Product for application generation. Third-party vendors sold VM-based databases, transaction monitors, and development tools. Today most customers run Linux on z/VM, taking advantage of the hypervisor’s small overhead and robust resource controls.

### Technical Highlights
- Minimum VM/370 could run in 256 KB of real storage; modern z/VM typically needs 2–4 GB for the hypervisor itself.
- Each guest can be capped to a slice of physical CPUs or allowed to span all available cores.
- Built-in service virtual machines handle TCP/IP, SCSI/FCP storage, and performance monitoring without special hardware.

## Schema Markup
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  "@type": "Thing",
  "name": "VM",
  "description": "Family of IBM virtual-machine operating systems dating from 1972 and still sold today as z/VM.",
  "url": "http://www.vm.ibm.com/",
  "sameAs": ["https://www.wikidata.org/wiki/Q15880542", "https://en.wikipedia.org/wiki/VM_(operating_system)"],
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## References

1. Freebase Data Dumps. 2013