What is CMS?
CMS provides functions for you to use at the terminal. It is an interactive environment. CMS is specifically designed to run on CP and depends on CP to interface with the resources. Therefore, unlike an operating system, CMS cannot operate independently on a real machine.
CMS provides terminal support, a file system, and a conversational command interface. (See Figure 1.) CMS also allows you to run programs written in standard programming languages, such as COBOL, PL/I, VS Pascal, FORTRAN, C/C++, and assembler. CMS is designed to make the whole programming process easier. You can plan, design, code, run, and test an application in your own virtual machine without interfering with anyone else. It is similar to having your own workstation.
Although it seems like you are the only one using CMS, many other virtual machines are using CMS, and you or your application can communicate and share data with these virtual machines. You or your application can even communicate with a virtual machine on another VM system or with another user or application on a non-VM system. (See Common Programming Interface (CPI) Communications.)