IBM System/360 20 User Manual

ITHE I!E]=RE~l]~~l_~YSI~~
Before any of the programs contained in the
program library of the tape-resident system
can be executed, a system run must be
initiated; i.e., the tape Basic Monitor
program must be loaaed from the system tape
into main storage. The loading of the
Basic Monitor program is performed by the
tape Initial Program Loader (IPL).
THE TAPE INITIAL PROGRAM LOADER
If the tape Initial Program Loader is to be
used, it must be contained in punched
cards. The IPL deck is preceded by a Clear
storage card. The IPL program is loaded
into main storage from the reading device
referred to as the loading unit. This
loading unit is the 2501 Card Reader or the
2520 Card Read-Punch or the primary feed of
the 2560 MFCM, whichever is attached.
A number of programmed halts may occur
during the loading and execution of the IPL
program. The code displays associated with
these halts and the appropriate restart
procedures are described in the section
E£Qg£am~~d-li~li_~i§£l~anQ_~~§i~£~
.!:£Q.£~g.!!£~§.
The IPL program loads the tape Basic Mon-
itor program into main storage from the
system tape mounted on SYSRES. Since there
is no standard assignment for SYSRES, an
ASSGN card for this symbolic device address
is required. (The tape drive assigned to
SYSRES must be a 9-track drive). The ASSGN
card must be placed directly behind the END
card of the IPL program deck, and in front
of the REP cards described in the following
section.
If a card reading device other than that
assigned in the tape Basic Monitor program
is to be used as SYSRDR, an appropriate
ASSGN card for SYSRDR must be placed behind
the ASSGN card for SYSRES.
The ASSGN card(s) must be followed eith-
er by an end-of-file card (/* in columns 1
and 2) or by REP cards followed by an ena-
of-file card.
Six REP cards (REP in cols. 2-4 ) and an
end-of-file card (/* in cols. 1-2) follow
the END card of the IPL program deck supp-
lied by IBM. They are used to furnish the
tape Basic Monitor in main storage with the
unit numbers of the tape drives attached to
the Model 20.
The REP cards supplied by IBM contain
the physical device addresses 0780 through
0785 in columns 17-20, where 07 is the
attachment point (valid for any magnetic
tape drive), and 80 through 85 are the unit
numbers to be inserted as standard numbers
for six drives (maximum number of tape
drives that can be attached to a Model 20).
The unit numbers (80-85) cannot be
inserted or changed by ASSGN cards sub-
mitted to the Job Control program. If the
unit numbers of the user's tape drives are
not 80-85, they can be inserted or changed
in one of the following ways:
1. by including ASSGN cards in the input
deck for the Load System Tape program
behind the tape Basic Monitor deck or,
if the tape Basic Monitor is read from
tape, behind the MONTE control card
(see the sections ~uiIQing_!~~Ini!i~l
~y§!em_Tap~_!£QID_l~M-~.!!E£li~Q-1fQg£am§
and ~Yilging_!ggitiQD~l_~Y§!g~Ta~g§
!£QID_1BM-~.!!EElied ~Dg_]§er=]£i!teD
R.fQg.f~ill'§) ;
2. by replacing the IB~-supplied REP cards
behind the tape IPL deck with REP cards
containing the unit numbers of the
user's tape drives in columns 17-20 •
In the first case (ASSGN cards submitted
to LDSYS), the standard assignments of the
tape Basic Monitor on the system tape are
inserted. The REP cards behind the IPL
deck may be removed to allow faster
processing.
In the second case (REP cards submitted
to the tape IPL) , the standard assignments
of the tape Basic Monitor in main storage
are inserted or changed. The Basic Monitor
program on the system tape is not affected.
!~ig-1: The REP cards indicate to the tape
Basic Monitor 6nly the attachment point and
the unit numters of the corresponding tape
drives. Therefore, if 7-track tape drives
or 9-track tape drives with compatibility
feature are assigned by means of REP cards
submitted to the IPL program, additional
ASSGN statements (submitted to the Job Con-
trol program) must be used for the appro-
priate tape characteristics specifications.
(For a list of these. specifications, see
the description of the ASSGN statement in
ltEl?gllgi~_!· )
Notg-1: If less than six tape drives are
attached and the standard assignments for
some or all of these drives are to be
inserted or changed by means of REP cards,
the user need replace only those REP cards
reguired to make the assignments for his
tape drives. The remaining REP cards must
be removed.
Initiation and Use of the Card-Resident and Tape-Resident Systems 13

IBM System/360 20 Specifications

General

Brand	IBM
Model	System/360 20
Category	Storage
Language	English