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PDP-10 Archives
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BB-BT99T-BB_1990
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10,7/system/devnam.hlp
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Device Names
TOPS-10 supports a number of peripheral input/output devices to handle
data acquisition, storage, retrieval, and display. These devices are:
Card Punch Card Reader DECtape
Disk Display Terminal Graphics Display
Hard-copy Terminal Line Printer Magnetic Tape
Paper Tape Punch Paper Tape Reader Plotter
The monitor allocates a device to your job when you request access to
the device. (See the ASSIGN and MOUNT commands.) Until you request a
device, it resides in the system pool of available resources.
To reference a device, you must specify a device name. The types of
device names are: generic, physical, logical, ersatz, and
system-defined logical.
Generic Device Names
The most general type of device name is the generic device name. When
you specify a generic name, the monitor selects a free unit of the
device type specified. When your computer is in a network
environment, the monitor chooses the device from those devices at your
location, or, if none are available, the monitor chooses the device
from the host (central) site.
A generic name can be two or three letters long and is followed by a
colon (:). Two-character generic names are less specific than
three-character generic names. For example, MT: means any magnetic
tape unit, but MTA: means any magnetic tape unit on controller A.
When you specify the generic name DSK: or DS:, the monitor uses your
job search list to determine which disk device should be selected for
you. For help on search lists, see the help file SERLST.
Generic Device Names
3-Letter 2-Letter
Device Device Name Device Name
Card punch CDP: CP:
Card reader CDR: CR:
Console terminal CTY: ---
DECtape DTx: DT:
Disk DSK: DS:
Packs DPx: DP:
RPx: RP:
Fixed head FHx: FH:
FSx: FS:
Display DIS: ---
Line printer LPT: LP:
lowercase/uppercase --- LL:
uppercase --- LU:
Magnetic tape MTx: ---
7-track --- M7:
9-track --- M9:
Operator terminal OPR: ---
Paper-tape punch PTP: PP:
Paper-tape reader PTR: PR:
Plotter PLT: ---
Pseudo-terminal PTY: ---
System library SYS: SY:
Terminal TTY: TT:
When you specify a generic name, the monitor selects the
lowest-numbered available unit of the device type specified. There
are two defaults when you specify a generic name:
1. When your program specifies DSK or DS, the system uses your
job search list.
2. When you specify TTY: or TT:, the monitor always selects your
terminal (assuming that these are not logical names).
Physical Device Names
Every I/O device has a physical name. This name consists of the
generic name, a letter indicating the controller, and one numeric
character indicating the unit number. For example, the generic name
MTA: indicates any magnetic tape unit on controller A. However, MTA1:
indicates magnetic tape unit 1 on controller A.
File Structures
The TOPS-10 operating system organizes disk devices into file
structures. File structures are logical arrangements of 128-word
blocks on one or more disk units. A file structure can exist on one
disk unit, or it can be distributed over several disk units designated
by a single name. However, two file structures cannot exist on the
same unit.
The operator or system administrator assigns a name to every file
structure when he or she defines the system's file structures. This
name is one to four characters long, and cannot duplicate a physical
device name, a unit name, or an existing file structure name. The
recommended names for public file structures are DSKA:,
DSKB:,...,DSKO: in order of decreasing speed.
File structures are illustrated and explained in detail in the TOPS-10
Monitor Calls Manual, Vol. 1.
Logical Device Names
You can assign a logical name to a physical device. The monitor will
recognize the name that you assign, and associate the logical name
with the physical device. You can assign a logical name to a device
using the ASSIGN command.
The logical name that you assign may be up to six alphanumeric
characters and may optionally be ended by a colon (:). Thereafter,
the monitor will use the device that you associated with the logical
name, when you or your programs specify that logical name. Logical
names are cleared by the DEASSIGN command. That is, use the DEASSIGN
command to disassociate logical names from devices. Logical names are
also cleared when you log off the system, and when you specify another
logical name for the same device.
Logical names are useful when you are writing a program that needs a
device, but you will not know until program execution what device you
will need. Use a logical name in the program to represent the device.
Before you run the program use the ASSIGN command to associate the
logical name with a physical device.
Logical names take precedence over physical names. Therefore, if you
assign the logical name DSK: to the device MTA3: (magnetic tape unit 3
on controller A), all output to generic DSK will go to the magnetic
tape.
Some names are recognized by the monitor as special system-defined
logical names that the monitor translates into physical device names.
One example is the generic device name OPR:. The generic name OPR: is
the system-default logical name for the operator's terminal.
Therefore, the terminal specified as OPR: can change during system
operation; but if you send a message to OPR:, the message will be
routed to the last physical device declared to be the operator's
terminal at your node.
All devices except terminals can be designated as being restricted
devices. You request a restricted device from the system pool of
available resources by issuing the MOUNT command. This command
requires operator intervention before the specified device is assigned
to your job. The system deassigns a restricted device from your job
when you log off the system or issue the DISMOUNT, DEASSIGN, or FINISH
command.
Unrestricted devices are assigned to your job on a first-come,
first-served basis when you issue the MOUNT or ASSIGN command. The
device assignment remains in effect until you release the device by
issuing a DEASSIGN command or a FINISH command, or you log off the
system.
The following example illustrates the use of both physical and logical
device names.
Example
You request a DECtape drive with the logical name ABC:
.ASSIGN DTA: ABC:
The monitor gives you unrestricted device DTA0: (DECtape number 0
on controller A). You then mount a DECtape on drive DTA0:
DTA0 ASSIGNED
You request any paper-tape punch and request that the logical
name ABC: be assigned to it.
.ASSIGN PTP: ABC:
The monitor prints a warning message, telling you that the
logical name was previously assigned to another device. The
monitor changes the logical-name assignment, so that the logical
name ABC: now refers to the paper-tape punch.
%LOGICAL NAME WAS IN USE, PTP0 ASSIGNED
You run the system program PIP.
.R PIP
You issue a command string to PIP asking that file FILEA.EXT be
transferred from device DTA0: to logical device ABC: (physical
device PTP0:).
*ABC:=DTA0:FILEA.EXT
You type a CTRL/C, returning your job to monitor mode.
*^C
You request another DECtape drive and request that logical name
DEF: be assigned to it.
.ASSIGN DTA: DEF:
The monitor prints a message telling you that all DECtape drives
are in use by the specified jobs. The monitor does not assign a
DECtape drive or a logical name to your job.
?ALREADY ASSIGNED TO JOB 13
You request that DECtape unit 0 (which you already have assigned
to you) be assigned the logical name DEF:.
.ASSIGN DTA0: DEF:
DECtape unit 0 takes on the logical name DEF:.
DTA0 ASSIGNED
You deassign the paper-tape punch, clearing the logical name
ABC:.
.DEASSIGN PTP:
You run the system program PIP.
.R PIP
You request that the file FILEB is to be transferred from device
DEF: to device ABC:
*ABC:=DEF:FILEB
TOPS-10 prints an error message indicating that the logical
device name ABC: is no longer assigned.
?DEVICE ABC DOES NOT EXIST
You type a CTRL/C, returning your job to monitor mode.
*^C
You request drive DTA0: (DECtape drive 0) again and request that
the logical DEF: be changed to XYZ:
.ASSIGN DTA0: XYZ:
The system disassociates the logical name DEF: from DTA0:.
DECtape unit 0 takes on the logical name XYZ:.
DTA0 ASSIGNED
Ersatz Device Names
An ersatz device is a disk-simulated library. Although you specify an
ersatz device like a file structure, an ersatz device represents a
particular project-programmer number on a disk structure. Ersatz
device names are three characters long. See the help file ERSNAM for
a complete list of the ersatz device names used by TOPS-10.