Sets up the $$B-transient area for use by DOS routines. DftSSET ----If-SET DOS OFF has been specified, issues the DI1GNOSE 64 PURGESYS function for the CftSDOS segment and, if VSlft has been loaded, for the segment. DftSSET: SET SYSNAftE PROCESSING Determines whether the name of the CftSSEG segment is being changed. DftSSET ---netermines whether NONSBARE is specified. If so, the segment may be
loaded and kept. If NONSBARE is not specified, the segment is purged,
because it is needed only on demand. Once a new name is placed in the SYSNAftES table replacing CftSSEG, the DIAGNOSE 64 FINDSYS function is issued to determine whether the new name has been entered correctly. If the FINDSYS is successful, the
size of the virtual machine is compared to beginning address of the
segment to determine whether the segment overlays virtual machine storage. D"SSET ---rf-the segment can be used (i.e. does not overlay the virtual machine storage) the DIAGNOSE 64 LOADSYS function is performed. If the LOADSYS executes successfully, control passes to D!SINT, where the
segment is purged (because it is only needed on demand). CMS Method of operation and Program Organization 2-61

Processing and Executing eMS Files As shown in Part 1 of Figure 9, the five general topics form the
category "Process and Execute CMS Files." Two of these topics are
discussed in this section: "Maintaining an Interactive Console
Environment" and "Loading and Executing TEXT files."
Maintaining an Interactive Console Environment Two levels of information are discussed in the following section. The
first level is a general discussion of how CMS maintains an interactive
console environment. The second level is a more detailed discussion of the methods of operation mainly responsible for this function. Console Management and Command Handling in CMS There are two major functions concerned with maintaining an interactive terminal environment for CftS: console management and command processing.
The CMS module that manages the virtual machine console is DftSINT. The
module responsible for command frocessing is DftSITS. ftany CftS modules
are called in support of these two functions but the modules in the
following list are primarily responsible for sUPForting the functions: DftSCRD ---aeads a line from the console. !H!SC!!! Writes a line to the console. converts a command line to PLIST format. Converts abbreviated commands to their full names. Passes a command line to CP for execution.
Maintaining an Interactive Command/Response
Session
Three main lines of control maintain the continuity for an interactive CMS session: (1) handling of commands passed to DftSINT by the
initialization module, DftSINS (2) handling of commands entered at the
console during a session, and (3) handling of co.mands entered as subset
commands. The following lists show the main logic paths for first two
functions.
2-62 IBM VM/370 System Logic and program Determination--Volume 2