Graphic Capabilities of Text Terminals
+ Many text terminals can display bit-mapped images, but not in
+color. Unfortunately, the popular image formats used on the Internet
+are not supported. The protocols for such graphics include: Tektronix
+Vector Graphics, ReGIS (DEC), Sixel (DEC), and NAPLPS (North American
+Presentation Level Protocol Syntax).
-
To a limited degree some ASCII symbols can provide graphics on
-text terminals. One may form arrows <--- and draw boxes with _ and
-|. With special graphic character sets, even more is possible. None
-of these are really graphics terminals. However, the term "graphics
-terminal" is sometimes applied to all text-only terminals since text
-is a limited form of graphics.
+Even without bit-mapped images, ordinary text terminals can sort of
+display images. One may form arrows <--- and draw boxes with _ and
+|. With special graphic character sets, even more is possible. By
+using all the letters, one may produce "ascii graphics" art. The term
+"graphics terminal" usually means a terminal that can display bit
+mapped images. However, this term is sometimes applied to all
+text-only terminals since text is a limited form of graphics.
-There are two basic types of graphics displays: raster and vector
+ Thin Clients (Terminals ?)
+
+ These are either terminals or thin (minimal) computers. In
+contrast to text-terminals, they all display a high-speed GUI. They
+are dependent on higher power computers (servers) for their operation.
+For a true terminal, the computing work and disk storage will all be
+done on the server. At the other extreme, most of this work and
+storage is done at the client but some things such as administration,
+still depend on the server. Since the client here is not "thin" it's
+not clear that this is really a thin client. Some claim that
+text-terminals are also thin clients.
+
+ Graphics Displays
+ There are two basic types of graphics displays: raster and vector
(rarely used). Raster graphics (bit-mapped) puts dots on the screen
by horizontal scan lines drawn by an electron beam (or by activating
-pixels or dots on a flat screen). Vector graphic displays are usually
-for monochrome screens that don't have any dots. They use smart
-electronics to draw lines and curves with an electron beam that can
-move in any direction (at any angle and location). Vector graphics
-draws high quality lines without zig-zags but is both rare and
-expensive. Raster graphics is almost universally used today. For
-PC's, images encoded in vector graphic format are sometimes used but
-they are translated to raster graphics format for display (with a drop
-in image quality).
+pixels or dots on a flat screen). Vector graphic displays were
+intended to be used for monochrome screens that don't have any dots.
+They use smart electronics to draw lines and curves with an electron
+beam that can move in any direction (at any angle and location). True
+vector graphics draws high quality lines without zig-zags but is both
+rare and expensive. Raster graphics is almost universally used today.
+For PC's, images encoded in vector graphic format are sometimes used
+but they are translated to raster graphics format for display (with a
+drop in image quality).
- Serial Line Graphics Terminals
- Most of this document also applies to these. Most of these can
-also function as text terminals. The protocols for such graphics
-include: Tektronix Vector Graphics, ReGIS (DEC), Sixel (DEC), and
-NAPLPS (North American Presentation Level Protocol Syntax).
+ Full Graphics Terminals (often known by other names)
+ None of these are covered in this document. A terminal that
+deserves to be called smart is a graphics terminal which can rapidly
+display full-screen graphics just like a PC monitor. It will also
+have a mouse. Bytes sent to it often represent bit-maps for pictures
+(and other graphics). It will often use a high-speed connection to
+its host computer using twisted pair or coax cable. X-Window
+terminals are such devices. See the link to Xterminal-HOWTO at [. So are some "thin
+clients" including ones which have a MS-Windows GUI which comes from a
+remote Windows Terminal Server.
-] Fast Graphics Terminals (often known by other names)
- None of these covered in this document. A terminal that deserves
-to be called smart is a graphics terminal which can rapidly display
-full-screen graphics just like a PC monitor. It will also have a
-mouse. Bytes sent to it often represent bit-maps for pictures (and
-other graphics). It will often use a high-speed connection to its
-host computer using twisted pair or coax cable. X-Window terminals
-are such devices. See the link to Xterminal-HOWTO at [
+For displaying the MS-Windows GUI, Citrix was (and is) a major player
+with what was called Winterm using it's WinFrame software (which
+supported Windows 3.1). Microsoft licensed some of this and then came
+out with Hydra (code name), also known as "Windows Terminal Server".
+It works with versions 4 or higher of MS Windows NT. Then other
+companies that had their own proprietary systems decided to support
+Microsoft's system.
-For displaying a MS-Windows GUI there are at various types of
-interfaces and terminals: Winterm using WinFrame software from Citrix
-is one. Another (based in part on Citrix's code) is Hydra (code name)
-by Microsoft, also known as "Windows Terminal Server" which works with
-versions 4 or higher of MS Windows NT. Citrix uses its ICA protocol
-and has created an add-on to Hydra known as pICAsso so that WinFrame
-(ICA) based terminals can use the Hydra system. Hydra is also
-multi-user. There is also the "MultiConsole Personal Terminal" by
-Unbounded Technologies and Tektronix had its own multi-user interface
-but will now support Hydra. A magazine article in 1997 called Winterm
-a "dumb terminal" but it's really pretty smart. Such terminals are
-often called "thin clients", but some thin clients are more that just
-terminals as they can execute Java code sent to them, etc.
+Citrix uses its ICA protocol and has created an add-on to Hydra known
+as pICAsso so that WinFrame (ICA) based terminals can use the Hydra
+system. There exits a Linux ICA client. Microsoft has substituted
+RDP (Remote Desktop Protocol) for ICA. Citrix has replaced WinFrame
+with MetaFrame which supports Windows 95 and is used in conjunction
+with "Windows NT Terminal Server Edition". There is also the
+"MultiConsole Personal Terminal" by Unbounded Technologies. Tektronix
+had its own multi-user interface but will now support Hydra.
-] Network Computers (NCs)
- These are neither true computers nor terminals but are something
-in-between. One type of network computer (NC's) is a computer with a
-CPU but no hard Disk. They are full-graphics and connect to a server
-computer. They are different from terminals since the programs they
-run execute on their own CPU chips. Java code may be sent to them for
-execution. IBM calls this a "Network Station". They should work on
-IP networks and might work under a server running Linux. Wintel
-established a "NetPC" which, unlike the above, is almost a PC
-computer. However, it has no removable disks so users can't install
-their own software or obtain copies of anything. For using the Sun
-JavaStation NC under Linux see the JavaStation-HOWTO released in Apr.
-24, 2000.
+The above is sometimes called "network computing" since the terminals
+and servers connect to each other over a network. Network computers
+are something different as described below.
-Although the promoters of NCs and related Window-Terminals projected
-that they would replace millions of PCs, it hasn't yet happened. A
-major reason is that PCs have come down in price in recent years so
-that they are often even cheaper than NCs, etc. Thus for terminals,
-the Text-Terminal still predominates.
+ Network Computers (NCs)
+These are neither true computers nor terminals but are something
+in-between. They are also a type of thin client. One type of network
+computer (NC's) is a computer with a CPU but no hard Disk. They are
+full-graphics and connect to a server computer. They are different
+from terminals since the programs they run execute on their own CPU
+chips. Java code may be sent to them for execution. IBM calls this a
+"Network Station". They should work on IP networks and might work
+under a server running Linux. Wintel established a "NetPC" which,
+unlike the above, is almost a PC computer. However, it has no
+removable disks so users can't install their own software or obtain
+copies of anything.
+
+ Thin Clients Under Linux
+ Linux provides NFS (Network File System) so that if ordinary
+computers (not thin clients) are connected to each other via a
+network, then a person on one computer can run programs on another
+computer. It works also with X-Windows so that one may see GUI images
+generated on another computer. Linux also allows a computer to be
+diskless (see Diskless-HOWTO) and boot over a network. Thus using a
+diskless computer which runs NFS is just like using a NC (Network
+Computer). It's not really a NC but it's emulating a type of NC.
+It's also sometimes referred to (incorrectly ?) as a "terminal".
+
+Thus if you have an old PC with an ethernet card (NIC) you may be able
+to use it as a NC. Even if it doesn't have a NIC, you could use it as
+a text-terminal. See [. So Linux too supports a type of thin client which is the
+subject of Thinclient-HOWTO. For using the Sun JavaStation NC under
+Linux see the JavaStation-HOWTO.
+
+] Hardware hookups
+ There are 3 different hardware arrangements for thin clients.
+One just uses a PC computer as a thin client by emulating a thin
+client. It really isn't a thin client but it behaves like one.
+Another type looks just like a text-terminal. It just looks like a
+monitor, with a connector for a keyboard and another connector for a
+network cable. It's a dedicated thin client and can't be used for
+anything else. The third type looks like a tiny computer. It uses a
+standard PC monitor and keyboard both of which plug into a small box
+which is a "thin" computer. This box provides an interface between
+the monitor/keyboard and the network.
+
+ History and the Future
+ Promoters of NCs and related Window-Terminals projected that they
+would soon replace millions of PCs. In 1998 about 700,000 thin
+clients were sold with about 27% of them being NCs. But in 1999 only
+about 600,000 thin clients were sold. A major reason that more were
+not sold is that PCs have come down in price in recent years so that
+they are often no more expensive. However, it's argued that even
+though thin clients may cost the same as PCs, the maintenance and
+administration costs are less. Note that thin clients sometimes
+replace text terminals instead of PCs.
Emulation on a PC
+
Since a PC has a screen and keyboard (as does a terminal) but also
has much more computing power, it's easy to use some of this computing
power to make the PC computer behave like a text terminal. This is
@@ -495,12 +554,12 @@ same quality of display). This wasn't always the case since around
costs for memory and processors, one could make a text terminal smart
for only about a 10% or 20% increase in hardware cost.
-The reasons that text terminals are not yet obsolete are:
+The reasons that text terminals are fully obsolete are:
- There is no satisfactory standard interface for smart graphics
- terminals. The MS Hydra system is for MS Windows NT, while X-Windows
- is not as efficient as it should be (and X-Windows terminals are too
- costly).
+terminals that can be used with Linux (but there is for MS Windows).
+However one can run a diskless PC under Linux on a network where the
+diskless PC is a substitute for a smart graphics terminal.
- Many people don't need full screen graphics.
- Text terminals are low in cost and allegedly take longer to
become obsolete, yet can give access to a much newer (and powerful)
@@ -1191,8 +1250,7 @@ to help determine if a terminal behaves correctly like a vt53, vt100,
vt102, vt220, vt320, vt420 etc. There is no documentation but it has
menus and is easy to use. To compile it run the configure script and
then type "make". It may be downloaded from:
. An alternate download
-site is:
+url="http://sunsite.unc.edu/pub/Linux/utils/console/">
The Linux Console
The console for a PC Linux system is normally the computer
@@ -1246,18 +1304,19 @@ ADM-1l; WANG 2110. Block mode is available for IBM and Wyse. It runs
on a Linux PC.
Make a non-Linux PC a terminal
+
Emulators exist which run on non-Linux PCs. They permit you to
use a non-Linux-PC as a terminal connected to a Linux-PC. Under DOS
there is which is non-free to
+url="http://www.hilgraeve.com/htpe/index.html"> which is non-free to
business. It can emulate vt-220. Turbosoft's (Australia) TTWin can emulate over 80 different
terminals under Windows.
For the Mac Computer there is emulation by Carnation Software
+url="http://www.carnationsoftware.com/carnation/HT.Carn.Home.html">
One place to check terminal emulation products is Shuford's site, but
it seems to lists old products (which may still work OK). The fact
@@ -1547,10 +1606,8 @@ server.
Multiport I/O Cards (Adapters)
Additional serial cards may be purchased which have many serial
ports on them called "multiport boards". These boards are not covered
-in this HOWTO but there is quite a lot of coverage in the Serial-HOWTO
-One company which had (in 1998) below average prices is .
+in this HOWTO but there is a list of them (with URLs) in the
+Serial-HOWTO.
Direct Cable Connection.
The simplest way to connect a terminal to a host computer is via a
@@ -2440,13 +2497,8 @@ In some older terminals, only the manual tells how to save. For many
of these you press Ctrl-S to save.
Set-Up Options/Parameters
- See the Teemworld's for a description of many of these parameter as used in
-terminal emulation. Emulation is often a little different than an
-actual terminal.
-What follows in this section describes some of the options which are
+ What follows in this section describes some of the options which are
available in the set-up menus of many terminals. Options are also
called parameters or features. Many options may be called "modes".
Setting options is often called "configuring". Many of these options
@@ -2879,7 +2931,7 @@ text-terminal.
If you don't have the getty you want check other distributions and the
.
If you are not using modem control lines (for example if you only use
@@ -2947,10 +2999,11 @@ process will be garbled and parity will be set wrong. Thus it doesn't
seem feasible to try to use 8-bit data bytes with parity.
getty (part of getty_ps)
- (This is from the old Serial-HOWTO by Greg Hankins)
-Add entries for /etc/gettydefs if there they aren't
-already there:
+ (Most of this is from the old Serial-HOWTO by Greg Hankins)
+For this getty one needs to both put entries in a configuration file
+and add an entry in /etc/inittab . Here are some example
+entries to use for your terminal that you put into the configuration
+file /etc/gettydefs .
# 38400 bps Dumb Terminal entry
@@ -2962,7 +3015,9 @@ DT19200# B19200 CS8 CLOCAL # B19200 SANE -ISTRIP CLOCAL #@S @L login: #DT19200
# 9600 bps Dumb Terminal entry
DT9600# B9600 CS8 CLOCAL # B9600 SANE -ISTRIP CLOCAL #@S @L login: #DT9600
+
Note that the DT number you use here must be the same as the DT
+number that you use in /etc/inittab .
+
If you want, you can make
-Make sure there is no /etc/default/{uu}getty.ttyS /etc/conf.{uu}getty.ttyS /etc/default/{uu}getty.ttyS
/etc/conf.{uu}getty.ttyS
/etc/inittab file to run
+ url="http://www.tuxedo.org/terminfo">
- "Termcap and Terminfo" is a book published by O'Reilly in
1988.
@@ -5201,23 +5256,18 @@ fly up into the air when taking apart a key switch.
name= "Shuford's Website"> at the University of Tennessee has a great
deal of useful information about text terminals.
- VT terminal information and history
--
+-
purchased the VT and Dorio terminal business from DEC. To get Specs
select either ADDS, VT, or DORIO links. Then select a "data
sheet" link. Then on the data sheet select the "Go to Specs" link.
--
Wyse is a major manufacturer of terminals. is a major manufacturer of terminals.
- For new models see See also
-
--
or
- is a list of escape sequences (and control
- codes) for some terminal emulations (including VT 100, 300, 420, and
- Wyse).
+ name="Wyse text-terminals database"> For current models see .
+-
is a list of escape sequences (and
+ control codes) for some terminal emulations (including VT 100, 300,
+ 420, and Wyse).
- comp.terminals is the newsgroup for terminals
@@ -5333,15 +5383,13 @@ escape sequences options will not be repeated here.
Esc Sequence List
For a list of many (but not all) escape sequences for various
-terminals see or . These are used for terminal emulation and are not
-always the same as on the corresponding real terminal..
-A list for VT (not maintained) may be found at . These are used for terminal
+emulation and are not always the same as on the corresponding real
+terminal. A list for VT (not maintained) may be found at . Search for "VT".
+name="Emulators FAQ">. Search for "VT". For downloading manuals see
+.
8-bit Control Codes
Table of 8-bit DEC control codes (in hexadecimal). Work on VT2xx or
@@ -5566,46 +5614,17 @@ located nearby, the need for high speed and longer distance
transmission was apparently not recognized.
Successors to EIA-232
- A number of EIA standards have been established for higher speeds
-and longer distances using twisted-pair (balanced) technology.
-Balanced transmission can sometimes be a hundred times faster than
-unbalanced EIA-232. For a given speed, the distance (maximum cable
-length) may be many times longer with twisted pair. But PC-s keep
-being made with the "obsolete" EIA-232 since it works OK with modems
-connected to slow telephone lines, and it works OK with mice.
-
-One exception is Apple's Mac computer with its EIA-232/EIA-422 GeoPort
-which provides twisted-pairs (balanced) for transmit and receive. It
-uses a small round "mini-DIN" connector. It also provides
-conventional EIA-232 but only at 5 volts (which is still legal
-EIA-232). However, due to the fact that Macs cost more than PC's,
-they are seldom used as a host computer for terminals. Some newer
-terminals use EIA-423 but this is just like the unbalanced EIA-232 and
-can be connected to a EIA-232 port. This EIA-423 is only 5 volts, but
-the specs call for higher speeds than the EIA-232 (which will be of no
-help on a long run where it's the unbalance that causes interference).
-
-EIA-485 is also balanced and is used as a "bus" like ethernet and USB.
-One device connected to it is the "master" and polls the "slaves" for
-input. Since many computers may share the twisted pair its sometimes
-called "multidrop". Another twisted pair is used for traffic from the
-master to the slaves. The output voltage on the pins must be tristate
-with the third state being open circuit to permit other units to use
-the "bus". It's been claimed that protocols are not standardized for
-multidrop and that's bad news. See
-
-EIA-530-A (balanced but can also be used unbalanced) at 2Mbits/s
-(balanced) was intended to be a replacement for EIA-232 but few have
-been installed. It uses the same 25-pin connector as EIA-232.
-
-
-The High Speed Serial Interface ( HSSI = EIA-612/613) uses a 50-pin
-connector and goes up to about 50 Mbits/s but the distance is limited
-to only several meters. The Universal Serial Bus (USB) is being built
-into PCI chips. It is 12 Mbits/s over a twisted pair with a 4-pin
-connector (2 wires are power supply) but it also is limited to short
-distances of at most 5 meters (depends on configuration).
+ See the Serial-HOWTO section "Other Serial Devices" for a longer
+discussion about non-EIA-232 ports. A number of EIA standards have
+been established for higher speeds and longer distances using
+twisted-pair (balanced) technology. Balanced transmission can
+sometimes be a hundred times faster than unbalanced EIA-232. For a
+given speed, the distance (maximum cable length) may be many times
+longer with twisted pair. Few terminals seem to support them. While
+many terminals also support EIA-423 is is almost like EIA-232 but is
+only 5 volts and somewhat higher speeds (without using twisted pair).
+Twisted pair includes EIA-422, EIA-530-A, HSSI (High Speed Serial
+Interface), USB (Universal Serial Bus), and of course ethernet.
Line Drivers
For a text terminal, the EIA-232 speeds are fast enough but the
@@ -5855,10 +5874,11 @@ Sometimes people erroneously think this is for an ethernet connection.
VT520: Supports full DTR/DSR flow control.
Wyse
- Wyse has some FAQ's for terminal numbers under 100 (such as WY60).
-See
-For the specs on more recent terminals see
-See .
+ For specs on terminals see . This
+will also lead to some FAQ's for terminal numbers under 100 (such as
+WY60). For the specs on more recent terminals see See .
Wyse 60
Display adjustments (must remove cover): Brightness VR202, Height