232 IBM VM/370 System Programmer's Guide

Introduction to eMS The Conversational Monitor System (CMS), the major subsystem of VM/370, provides a comprehensive set of conversational facilities to the user. Several copies of CMS may run under CP, thus Froviding several users
with their own time sharing system. CMS is designed specifically for
the VM/370 virtual machine environment.
Each copy of CMS supports a single user. This means that the storage
area contains only the data pertaining to that user. Likewise, each CMS user has his own machine configuration and his own files. Debugging is
simpler because the files and storage area are protected from other
users. Programs can be debugged from the terminal. The terminal is used as
a printer to examine limited amounts of data. After examining program
data, the terminal user can enter commands on the terminal that will
alter the program. This is the most common method used to debug
programs that run in CMS. eMS, operating with the VM/370 Control Program, is a time sharing
system suitable for problem solving, program development, and general
work. It includes several programming language processors, file
manipulation commands, utilities, and debugging aids. Additionally, ces provides facilities to simplify the operation of other operating systems
in a virtual machine environment when controlled from a remote terminal.
For example, CMS capabilities are used to create and modify job streams,
and to analyze virtual printer output. Part of the CMS environment is related to the virtual machine
environment created by CP. Each user is completely isolated from the
activities of all other users, and each machine in which CMS executes
has virtual storage available to it and managed for it. The CP commands
are recognized by CMS. For example, the commands allow messages to be
sent to the operator or to other users, and virtual devices to be
dynamically detached from the virtual machine configuration.
The CMS Command language
The CMS command language offers terminal users a wide range of
functions. It supports a variety of programming languages, service
functions, file manipulation, program execution control, and general
system control. The CMS commands that are useful in debugging are
discussed in the "Debugging with CMS" section of "Part 1. Debugging with YM/370." For detailed information on all other CMS commands, refer to
the gDg Figure 28 describes CMS command processing. Part 3. Conversational Monitor System (Ces) 233