What is meant by a virtual machine operating system?

What is the difference between a virtual machine and a virtual machine operating system? I thought all VMs were operating systems. I came across the phrase here:

Quote:

---

VM (often: VM/CMS) refers to 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

---

A Virtual Machine is typically software that emulates a computer.
A VM OS is an operating system that runs inside the VM.
But don't quote me on that.

A Virtual Machine Operating System is a server operating system that provides virtual machine services to its clients.

See VM/CMS.

Quote:

---

Originally Posted by Elysia

A Virtual Machine is typically software that emulates a computer.
A VM OS is an operating system that runs inside the VM.
But don't quote me on that.

---

...

:wink: