IBM System/370 145 Manual page 180

The emulator program generated will emulate, without change,
1400/1010 programs written in accordance with IBM 1400/7010 Principles
of Operation manuals, subject to the following conditions:
• 1400/1010 programs that purposely depend on the absence of a
1400/1010 feature or on error conditions may not execute properly.
• Programs with wldetected programming errors and those that depend on
timing of 1400/7010 I/O operations yield unpredictable results.
An emulator program is handled by DOS in the same manner as any
problem program. When using the 1401/1440/1460 emulator, 1400 programs
may be cataloged to, and fetched from, a core image library for
execution or loaded from a card, tape, or direct access storage device;
1410/1010 programs can
be
loaded only from a card, tape, or direct
access storage device. standard DOS job control statements are
used
to
prepare the system for an emulator job. The EXEC job control statement
causes the specified emulator program to be loaded, and control is
passed to the emulator program. Emulator control statements are read by
the emulator from the logical unit selected at generation time.
Emulation with the 1401/1440/1460 and 1410/1010 emulators consists of
three main steps:
1. Initialization. Emulator control statements supplied by the user
are read and interpreted. This information overrides, for the
execution of the emulator, information specified at emulator
generation.
2. Loading (or fetching - 1401/1440/1460). The 1400/7010 program is
loaded from a card reader, magnetic tape, or direct access
storage device. For the 1401/1440/1460
emulato~,
a 1400 program
can be fetched from a core image library if i t has been
cataloged.
3.
Execution (or precataloging - 1401/1440/1460). When loaded, the
1400/1010 program is executed. The 1400/7010 instructions are
fetched, interpreted, and executed by the emulator until an end-
of-job condition is recognized. For the 1401/1440/1460 emulator,
the 1400 program can be either executed or converted into a DOS
object module (precataloged). This module can
be
subsequently
link-edited and cataloged in a core image library.
Input/output errors are processed by DOS device error recovery
procedures. Input/output errors that cannot be corrected, such as
permanent input/output errors and wrong-length records, are passed to
the 1400/1010 program.
Console simulation and operator communication with the emulators are
provided by the eXChange of emulator commands and messages between the
operator and the emulators. The emulators provide messages to inform
the operator of errors or other conditions that require his attention or
a response. Emulator commands can be entered from the console printer-
keyboard and are handled in the same way as operator communications are
currently handled by DOS.
Tape and Disk Emulation
The user has the option of processing tape files in 1400 format or in
spanned variable-length record format. Two tape formatting programs--
the Tape Preprocessor and Tape Postprocessor--are available to convert
tape files from 1400 format to spanned record format, and vice versa;
1410/1010 tapes containing records larger than 32K must be converted to
spanned record format prior to emulation. Mixed-density tapes are not
supported by the emulators or the tape formatting programs.
110
A Guide to the IBM System/370 Model 145