Terminal Fallback Facility — VMS 5.2
Additional information available:
About TFF
Terminal Fallback Facility (TFF)
The VMS Terminal Fallback Facility (TFF) provides table-driven
character conversion for terminals. The conversion is done
transparent to the application (unnoticed by the application
software unless explicit inquiries are made). You can choose
character conversion tables from a master character library, located
on the VMS system disk in:
SYS$SYSTEM:TFF$MASTER.DAT
This library contains all the character tables supported by TFF.
Conversions can be one character to many on output to a terminal,
and one to one on input from a terminal.
TFF can also perform character compose emulation on input.
Furthermore, you can control which keys are auto-compose keys.
One of the applications of TFF is to allow users with National
Replacement Character (NRC) set terminals to use software developed
with the Digital Multinational Character Set (MCS). MCS is
essentially the ASCII character set plus 128 characters currently
used by owners of NRC terminals around the world.
Commands
After you invoke TFU, you can enter any of the TFU commands. These commands follow the standard rules for DCL commands. For example, to view the list of character tables on line, enter the following commands: TFU> SET LIBRARY SYS$SYSTEM:TFF$MASTER.DAT TFU> DIRECTORY
Additional information available:
DIRECTORY
Provides a directory of a TFF library file. You can specify
selective, brief, or full directory listings.
If you specify a library name, that library becomes the current work
library.
Format: DIRECTORY [library-name]
Additional information available:
Parameter
library-name Indicates the name of the library for which a directory listing is requested. If you have already established a work library, the library-name is optional. If you do not specify a library name, the default file specification is: SYS$DISK:[].DAT
Qualifiers
Additional information available:
/ALL
/ALL Lists all tables in the target library.
/COMPOSE
/COMPOSE Lists only compose sequence tables. You cannot use /COMPOSE simultaneously with /ALL or /FALLBACK.
/FALLBACK
/FALLBACK Lists only fallback tables. This is the default for the DIRECTORY command. You can not use /FALLBACK simultaneously with /ALL or /COMPOSE.
/FULL
/FULL Displays more detailed table information. By default, only one line of information is displayed about each table you select.
Examples
1. TFU> DIRECTORY SYS$SYSTEM:TFF$MASTER.DAT/FALLBACK/FULL
Directory of TFF library SYS$COMMON:[SYSEXE]TFF$MASTER.DAT;1
Name Type Base Description
---- ---- ---- -----------
ASCII Fbk MCS MCS for ASCII (US)
ASCII_OVST Fbk MCS MCS for hardcopy ASCII terminal (overstrike)
BRITISH Fbk MCS MCS for British NRC(BS 4730 [ISO 646 variant])
CANADIAN Fbk MCS MCS for French-Canadian NRC (CSA Z243.4-1985)
.
.
.
SWEDISH_D47 Fbk MCS MCS for Swedish NRC (old type D47)
SWEDISH_E47 Fbk MCS MCS for Swedish NRC (SEN 85 02 00 - E47)
SWISS_VT102PY Fbk MCS MCS for Swiss VT102PY
TURKISH Fbk MCS MCS for Turkish NRC (partial ISO 6937/2)
VT100_MCS Fbk MCS MCS for VT100s with DEC-Supp in ROM#1
YUGOSLAVIAN Fbk MCS MCS for Yugoslavian NRC (JUS I B1.002)
A total of 28 tables
TFU>
This example shows how to produce a brief directory listing of all
the fallback tables in the current work library.
2. TFU> DIRECTORY SYS$SYSTEM:TFF$MASTER.DAT/FALLBACK/FULL
Directory of TFF library SYS$COMMON:[SYSEXE]TFF$MASTER.DAT;1
Name Type Base Description
---- ---- ---- -----------
ASCII Fbk MCS MCS for ASCII (US)
Table edit level: V1.0-0
Size (in bytes): 1128
Table format version: 0
ASCII_OVST Fbk MCS MCS for hardcopy ASCII terminal (overstrike)
Table edit level: V1.0-0
Size (in bytes): 1352
Table format version: 0
BRITISH Fbk MCS MCS for British NRC (BS 4730 [ISO 646 variant])
Table edit level: V1.0-0
Size (in bytes): 1128
Table format version: 0
.
.
.
.
VT100_MCS Fbk MCS MCS for VT100s with DEC-Supp in ROM#1
Table edit level: V1.0-0
Size (in bytes): 1413
Table format version: 0
YUGOSLAVIAN Fbk MCS MCS for Yugoslavian NRC (JUS I B1.002)
Table edit level: V1.0-0
Size (in bytes): 1128
Table format version: 0
A total of 28 tables
TFU>
This example shows how to display full information about all
fallback tables in the library SYS$SYSTEM:TFF$MASTER.DAT.
LOAD
LOAD TABLE
Loads a table from the current work library into nonpaged dynamic
memory pool. Before you use this command, the fallback driver,
FBDRIVER, must be loaded into memory by means of the System
Generation Utility (SYSGEN) or SYS$MANAGER:TFF$STARTUP.COM. A table
must be loaded into nonpaged dynamic memory pool before it can be
used.
The following tables are always present and cannot be loaded or
unloaded:
ASCII - Fallback
LATIN_1 - Compose sequence validation
Format: LOAD TABLE table-name
Additional information available:
Parameter
table-name Indicates the name of the table to be loaded.
Example
1. TFU> LOAD TABLE HEBREW_VT100 This example shows how to load table HEBREW_VT100 into nonpaged dynamic memory pool from the current work library.
SET
Defines or changes fallback libraries, tables, and terminal
characteristics.
Format: SET option
Additional information available:
DEFAULT_TABLE
Establishes a default table for the system. Before you specify a
table as the system default, you must load the table into nonpaged
dynamic memory pool using the LOAD command. The SET DEFAULT_TABLE
command reads the table type (fallback or compose) from the
specified table's header and makes the target table the default for
its type.
Before you enable any defaults, the following defaults apply:
ASCII - Fallback
LATIN_1 - Compose validation
Format: SET DEFAULT_TABLE table-name
Additional information available:
Parameter
table-name Indicates the name of the table to be the default table.
Examples
1. TFU> SET DEFAULT_TABLE HEBREW_VT100
TFU> SHOW DEFAULT_TABLE
System default TFF tables are:
HEBREW_VT100 (fallback)
LATIN_1 (compose sequence validation)
TFU>
The command in this example established HEBREW_VT100 as the default
fallback table for the system. The table HEBREW_VT100 must be loaded
prior to issuing this command.
2. TFU> SET DEFAULT_TABLE LATIN_1
TFU>
Because the LATIN_1 table is a compose sequence validation table
rather than a fallback table, the command in this example makes the
LATIN_1 table the default compose sequence validation table.
LIBRARY
Allows you to declare a work library. Note that some commands
implicitly declare a work library. If the library is located it
becomes the new work library.
Format: SET LIBRARY library-name
Additional information available:
Parameter
library-name Indicates the name of the library to be made the current library. You must specify a library with the SET LIBRARY command.
Example
1. TFU> SET LIBRARY SYS$SYSTEM:TFF$MASTER.DAT
TFU> LOAD HEBREW_VT100
In this example, the first command sets the library to be
SYS$SYSTEM:TFF$MASTER.DAT which is the default file name and
location. This command directs TFF to use character conversion
tables located in that file. The second command loads the table
HEBREW_VT100 into nonpaged dynamic memory pool.
TERMINAL
TERMINAL/FALLBACK
Enables or modifies TFF terminal parameters. The /FALLBACK qualifier
is required, but you can place it before or after the terminal-name
parameter.
SET TERMINAL/NOFALLBACK takes no options and is equivalent to SET
TERMINAL/FALLBACK=TABLE:NONE.
Format: SET TERMINAL /FALLBACK[=(Option,...)] [terminal_name]
SET TERMINAL/NOFALLBACK [terminal-name]
Additional information available:
Parameter
terminal-name
Indicates the target terminal for the set operation. If not
specified, your own terminal is used. Note that you can use TFF only
from local terminals; you cannot use terminal fallback on a remote
terminal (RTAx), the fallback terminal device (FBA0), a Packet
Switch Interface (PSI) terminal (NVA0), a disconnected virtual
terminal, or a terminal set for dynamic switching (DYNSWITCH) with
DECnet.
You can use TFF locally and then use the DCL command SET HOST to
access a remote system.
option
Modifies the terminal parameters. If you specify more than one,
enclose them in parentheses, and separate each with commas. You can
use the following options with the FALLBACK=option qualifier:
Option Definition
[NO]ACCEPT Enables input of 8-bit characters if the
terminal is capable of generating 8-bit
characters. The default is 7-bit character
generation. 7-bit terminals, such as VT1xx
and LA1xx, should have this feature turned
off whereas VT2xx terminals may have it on
(depending on the active table). The NOACCEPT
option causes TFF to clear the eighth bit.
[NO]AUTOCOMPOSE Enables or disables all auto-compose keys
available for the fallback table associated
with a terminal. The AUTOCOMPOSE and
NOAUTOCOMPOSE options override any keys
specified with the ENABLE and DISABLE options
described next.
DISABLE=(value[,...]) Disables one or more active auto-compose
keys. Keys are chosen from the list of keys
available for the fallback table associated
with a terminal. The value argument is a list
of the decimal values of the keys to disable.
If you specify more than one value, separate
the values with commas and place them in
parentheses. SHOW TERMINAL/FALLBACK lists the
currently active keys and their decimal
values.
ENABLE=(value[,...]) Enables one or more auto-compose keys. Choose
keys from the list of keys available for the
fallback table associated with the specified
terminal. The value argument is a list of the
decimal values of the keys to enable. If you
specify more than one value, separate the
values with commas and place them in
parentheses. SHOW TERMINAL/FALLBACK lists the
currently active keys and their decimal
values.
GX_DEFAULT:gx-name Defines as the default character set the name
of a character set, previously defined and
stored in Read Only Memory (ROM) of the
specified terminal. For example, VT100LD
specifies the line drawing alternate
character set available on VT100 terminals,
and DECSUPP specifies DIGITAL's supplemental
character set.
These options are available for a variety of
incompatible terminals. For example, the
ASCII option applies to a special class of
older DIGITAL terminals that do not have an
ASCII ROM that allows display of the full
ASCII character set. These terminals have
only the NRC set of characters.
Currently you can specify any of the
following character sets for the default:
ASCII, CANADA, CANADA_2, DECSUPP, FINLAND,
FINLAND_2, FRANCE, GERMANY, ITALY, JIS,
NETHERLAND, NORDAN, NORWAY, NORWAY_2, SPAIN,
SPECIAL1, SPECIAL2, SPECIAL3, SWEDEN,
SWEDEN_2, SWISS, TCS, UK, or VT100LD.
For more information about available default
and alternate ROM-based character sets, see
the documentation for your specific
terminal.
[NO]SIGNAL Enables the output of a BELL character to
sound a terminal bell when an invalid compose
sequence is entered. This is the default. You
can disable this feature for applications
that split escape sequences (for output) into
two or more QIOs, because the BELL character
may destroy such a sequence.
[NO]SOFT_COMPOSE Enables software emulated compose, using the
terminal's compose sequence validation table.
You can enter compose sequences either by
pressing CTRL/K followed by the sequence, or
by pressing an auto-compose key followed by
the second character of the sequence.
[NO]SUSPEND Suspends or resumes TFF intervention. In
command procedures that perform data
transfers over the terminal line, use the
SUSPEND option to avoid having to remember
which TFF parameters to be reset. The SUSPEND
option suspends TFF intervention until you
specify NOSUSPEND.
TABLE:table-name Indicates the name of the fallback table to
enable. If you omit the table-name option and
the terminal does not yet have fallback
enabled then the system default is used.
Otherwise, no change is made to the
terminal's table. Specify NONE for the table
to disable fallback for the target terminal.
This is equivalent to SET
TERMINAL/NOFALLBACK.
Before you can enable it, the target table
must be present in nonpaged dynamic memory
pool. Use the SHOW TABLES command for
information about what tables are available.
TERMINAL:terminal_type Specifies the terminal type, as seen by TFF.
The terminal type controls part of the escape
sequence parsing done by TFF. Thus, you
should set this to the correct value. Use one
of the following values: VT100, VT102, VT200,
or AL_ARABI. VT102 also includes the
terminals that are named VT100xy, such as
VT100WF.
Examples
1. TFU> SET TERMINAL/FALLBACK=(ACCEPT, NOSIGNAL) The command in this example enables fallback using system defaults, if they are not already enabled. The option ACCEPT enables input of 8-bit characters; NOSIGNAL disables the terminal bell that sounds when invalid compose sequences are entered. 2. TFU> SET TERMINAL TXB0: /FALLBACK=TABLE:NONE The command in this example disables fallback for terminal TXB0. This is the same as SET TERMINAL/NOFALLBACK TXB0. Note that you can place qualifiers before or after the terminal-name parameter.
SHOW
Displays information about fallback tables and libraries.
Format: SHOW option
Additional information available:
DEFAULT_TABLELIBRARYSTATISTICSTABLESTERMINAL
DEFAULT_TABLE
Displays the default fallback tables for your system.
Format: SHOW DEFAULT_TABLE
Additional information available:
Example
1. TFU> SHOW DEFAULT_TABLE
System default TFF tables are:
CANADIAN (fallback)
LATIN_1 (compose sequence validation)
TFU>
The command in this example displays the default fallback and
compose tables as they were established before the command was
entered. In this example, the table CANADIAN is the default fallback
table, and the table LATIN_1 is the default compose sequence
validation table.
LIBRARY
Provides information about the current work library.
Format: SHOW LIBRARY
Additional information available:
Example
1. TFU> SHOW LIBRARY
%TFF-I-READIS, Current input library is
SYS$COMMON:[SYSEXE]TFF$MASTER.DAT;1
TFU>
The command in this example displays the current work library. In
this case, the default library TFF$MASTER.DAT is listed.
STATISTICS
Displays memory and other statistical information related to TFF.
Format: SHOW STATISTICS
Additional information available:
Example
1. TFU> SHOW STATISTICS
TFF system statistics:
Memory (bytes) -
Fixed memory:
FBDRIVER 5608
Loaded tables:
Compose tables (0) 0
Fallback tables (2) 2288
Memory allocated by fallback terminals (0):
FBKs 0
Replaced vectors 0
Total memory used (bytes): 7896
Misc -
Total tables loaded since boot: 2
System default TFF tables are:
CANADIAN (fallback)
LATIN_1 (compose sequence validation)
The command in this example displays information about TFF use. From
this display you can see that two fallback tables have been loaded
(in addition to the default table), no new compose tables have been
loaded, and no fallback terminals have memory allocated to them.
Other information is also displayed.
TABLES
Displays information about all loaded TFF conversion tables.
Format: SHOW TABLES
Additional information available:
Example
TFU> SHOW TABLES
The following TFF tables are currently loaded
Name Type Base Crefc Trefc
---- ---- ---- ----- -----
ASCII Fbk MCS * 0 0
LATIN_1 Cmp MCS * 0 0
HEBREW_VT100 Fbk Hebr 0 0
CANADIAN Fbk MCS 0 0
%TFF-W-NOMORETAB, No more tables in wildcard scan
TFU>
This example shows how to display a line of information about the
table ASCII, loaded into nonpaged dynamic memory pool.
TERMINAL
TERMINAL/FALLBACK
Displays TFF statistics about a specific terminal. The /FALLBACK
qualifier is required, but you can place it before or after the
terminal-name parameter.
Format: SHOW TERMINAL /FALLBACK [terminal-name]
Additional information available:
Parameter
terminal-name Indicates the target terminal for the show operation. If excluded your own terminal is used. Note that you can only use TFF from local terminals; you cannot use terminal fallback on a remote terminal (RTAx), the fallback terminal device (FBA0), a Packet Switch Interface (PSI) terminal (NVA0), a disconnected virtual terminal, or a terminal set for dynamic switching (DYNSWITCH) with DECnet.
Qualifiers
Additional information available:
/ESCAPE_STATE/FLAGS/FULL/STATISTICS/TABLES
/ESCAPE_STATE
/ESCAPE_STATE Displays information about escape sequence parsing, and triggering Read Only Menories (ROMs). Use this information to debug your application.
/FLAGS
/FLAGS Displays which TFF terminal flags (options) can be set by the user and displays any internal TFF flags.
/FULL
/FULL Displays full information about the terminal. You cannot use this qualifier with /ESCAPE_STATE or /STATISTICS.
/STATISTICS
/STATISTICS Displays statistics about the specified terminal.
/TABLES
/TABLES Displays THE names of tables assigned to the specified terminal, including auto-compose keys for the fallback table.
Example
1. TFU> SHOW TERMINAL TXB0: /FALLBACK/FULL
TFF status for physical terminal _TXB0:
Active tables:
ASCII (FALLBACK)
LATIN_1 (compose sequence validation)
Autocompose-keys (Parenthesized values are character's decimal value):
None
Settable flags:
Nosuspend, Noaccept_8bit, Soft_compose, Signal, NoGR_terminal
Internal state flags:
None
Rom(s) that will trigger TFF I/O conversion:
ASCII
Escape sequence parsing states:
Input_state: Off (0), Output_state: Off (0)
Terminal graphic registers for the next character (setup = VT00):
G0 = ASCII, G1 = ASCII
Output mapping:
GL = G0 (maps 7-bit; 8th bit is truncated)
Output formatter expansion:
Received: 4579 Transmitted: 4579 Expansion rate: +0.0%
Replaced vector sizes (bytes):
Port vector: 99, Class vector: 139)
TFU>
This example shows how to produce a full display of TFF information
for terminal TXB0.
UNLOAD
UNLOAD TABLE
Unloads a table from nonpaged dynamic memory pool, releasing all
memory used by the specified table. You can only unload tables that
are not currently referenced by users and that are not the system
default table. You must log out or enter SET TERMINAL/NOFALLBACK
from your terminal to release a table for unloading. Note that you
cannot unload the ASCII and LATIN_1 tables.
Format: UNLOAD TABLE table-name
Additional information available:
Parameter
table-name Indicates the name of the table to be unloaded.
Example
1. TFU> UNLOAD TABLE HEBREW_VT100 The command in this example unloads table HEBREW_VT100 from nonpaged dynamic memory pool.