2. Use your terminal's Attention key (or equivalent). On a 2741
terminal, you must normally press the Attention key twice, quickly,
to enter the CP environment.
The following message indicates that your virtual machine is in the CP environment: CP After entering whatever CP commands you
virtual machine to the environment or mode
the CP command:
cp begin
need to use, you return your
that it came from by using
which, literally, begins execution of your virtual machine.
The eMS Environment You enter the CMS environment from CP by issuing the IPL command, which
loads CMS into your virtual storage area. If you are planning to use CMS for your entire terminal session,· you should not have to IPL again
unless a program failure forces you into the CP environment. When you issue the IPL command, you can specify either the named
system CMS at your installation or you can load CMS by specifying the
virtual address of the disk on which the CMS system resides. For
example:
cp ipl cms
-- or --
cp ipl 190 When your virtual machine is in the CMS environment, you can issue
any CMS command and any of the CP commands that are valid for your user
privilege class. You can also execute many of your own as or DOS programs; the ways you can execute programs are discussed in "Section 8.
Developing OS Programs Under CMS" and "Section 9. Developing DOS programs Under CMS." You can enter CP commands from CMS in any of the following ways: • Using the implied CP function of CMS (See • With the CP command • with the tcp function For the most part, you may enter any CP command directly from
the CMS environment. This implied CP function is controlled by an
operand of the CMS SET command, IMPCP. You can determine whether the
implied CP function is in effect for your virtual machine by entering
the command:
query impcp
If the response is: IMPCP = OFF you can change it by entering:
set impcp on
18 IBM VM/370 CMS User's Guide

When the implied CP function is set off, you must use either the CP command or the tcp function to enter CP commands from the CMS environment. CP commands that you execute in EXEC procedures must
always be prefaced by the CP command, regardless of the implied CP setting. An example of using the CP command is:
cp close punch When you issue CP commands from the CMS environment either
implicitly or with the CP command, you receive, in addition to the CP response (if any), the CMS ready message. If you use the tcp function, discussed next, you do not receive the ready message. You can preface any CP command line with the characters "tcP", followed by one or more blanks. When you enter a CP command this
way, the command is processed by CP immediately; it is as if your
virtual machine were actually in the CP environment.
EDIT, INPUT, AND CMS SUBSET The CMS editor is a VM/370 facility that allows you to create and
modify data files that reside on CMS disks. The editor environment, more commonly called the edit environment, is entered when yOU issue
the CMS command EDIT, specifying the identification of a data file you want to create or modify.
edit myfile assemble
is an example of how you would enter the edit environment to either
create a file called MYFILE ASSEMBLE or to make changes to a disk
file that already exists under that name. When you enter the edit environment your virtual machine is
automatically in edit mode, where you can only issue EDIT subcommands
or CP commands prefaced by "tcP." EDIT subcommands tell the editor
what you wish to do with the data you have accessed. After you enter
the EDIT subcommand:
input
data lines tnat you enter are considered input to
return to edit mode, you must enter a null line.
If you issue the EDIT subcommand:
ems
the editor responds: CMS SUBSET the To
and your virtual machine is in CMS subset mode, where you can issue any valid eMS subset command, that is, a CMS command that is allowed
in CMS subset mode. These include: ACCESS CP DISK ERASE EXEC HT
LISTFILE PRINT PUNCH QUERY READCARD
RT SET STATE STATEW TYPE Section 2. VM/310 Environments and Mode Switching 19