While the common monochrome terminal is not a color terminal it may have a fixed "color" display other than white such as green or amber. All terminals have black (electron beam turned off = zero brightness). A real color terminal can change the color of the text and background to many different colors while a monochrome terminal can only change the brightness of a fixed color.
However, changing the brightness, etc. gives a lot of possibilities. For example, a black and white (monochrome) terminal can have white, grey, and black by varying the brightness. Some words can be black on a light grey background while other are highlighted by black on white. In addition there is white on black, underlining, and blinking.
Color works like the color on a computer monitor or TV screen. The CRT has three colors of dots on it with each color controlled by its own electron beam (3 beams). Monochrome has inherently better resolution since it doesn't depend on dots permanently fixed on the screen. For text terminals the only use of color is to differentiate text and this advantage is not always worth the cost of worse resolution. Thus monochrome may be better since it also costs less.
For this the terminal has two serial ports. Each port is connected to a serial port on a different computer. Thus one may log in to two different computers with each session displaying in a split-screen window. Alternatively, each session may run full-screen with a "hot" key (or the like) to switch between sessions. One could also connect to two different serial ports on the same computer and log in twice (similar to "virtual terminals" at the console).
The terminal has two serial ports as above but the two ports are not identical in behavior. If a printer is connected to the printer or auxiliary port, then pressing certain keys will print the screen. One may also have everything that displays on the screen go also to the printer. If the port is an auxiliary port one may connect this to another computer and almost have dual sessions as above. However, the video memory inside the terminal may not retain both sessions so you may need to refresh the screen when switching to the other session. There will likely not be a hot key either but possibly a programmable function key may be programmed to do this.
There exists various key combinations and escape sequences for controlling such a port. It may be difficult to find out how to use this port without having a terminal manual.
A character-set is normally represented by a list (or table or chart) of characters along with the byte code assigned to each character. The codes for a byte range from 0 to 255 (00 to FF in hexadecimal). In MS-DOS, character-set tables are called "code-pages". You should examine such a table if you're not familiar with them. They are sometimes included in printer and terminal manuals but may be difficult to find.
ASCII is one of the most common character-sets used on text terminals. It is a 7-bit code but can be made into 8-bit if the first bit (high order bit) is always set to 0. Other character-sets are usually available (except on very old terminals where the only choice is ASCII). The first half of most character-sets are the conventional ASCII characters and the second half (the characters with the high-order bit set to 1) belong to a wide variety of character-sets. Character sets are often ISO standards. To get a non-ASCII character set on a terminal, you likely need to download a soft-font for that character-set into the memory of the terminal.
Besides ASCII, there are some other common character-sets, all 8-bit. CP stands for Code Page character sets invented by IBM: CP-437 (DOS ECS), CP-850 (Multilingual Latin 1 --not the same as ISO Latin-1), ISO-8859-1 (Latin-1), ANSI (derived from Latin-1). MS Windows uses ANSI while the Internet often uses Latin-1. There are several ISO-8859 character sets in addition to Latin-1. These include Greek (-7), Arabic (-6), Eastern European (-2), and Russian (-5). There are many others. For example, KOI8-R is more commonly used for Russian than IS0-8859-5. Unicode is a very large character-set where each character is represented by 2 bytes instead on just one byte.
Websites re character-sets are:
Most terminals made after the mid 1980's can accept downloaded soft-font. This means that they can display almost any character set provided that you can find the soft-font for it. If you can't find the needed soft-font, you can always create your own. A font editor for this is called BitFontEdit (written by the author of this document) and might be found at http://www.cs.utk.edu/~shuford/terminal_index.html
Terminal keyboards often have a number of keys that one doesn't find on a PC keyboard. Few (if any) actual terminals will have all of these keys and most will have additional keys not listed here. Some have a large number of special purpose keys such as terminals made for use with cash registers. There are often many more key meanings than shown here since these keys often have extended meanings when used in conjunction with other keys (such as shift and control).
The console for a PC Linux system is the computer monitor It emulates a terminal of type "Linux". The emulation is flexible and has features which go well beyond those of the vt100 terminal it emulates. These include the ability to use custom fonts and easily remap the keyboard (without patching the source code and recompiling the kernel as is required for the case of a real terminal). These extra features reside in the console driver software and not in the emulation software but the results are like it was part of the emulation. Many commands exist (see Keyboard-and-Console-HOWTO, formerly just Keyboard-HOWTO) to utilize these added features. Real terminals, which use neither scan codes nor VGA cards, unfortunately can't use most of these features. One may recompile Linux to make a terminal receive the messages which normally go to the console (see Make a Terminal the Console).
Many messages from the system are normally only sent to the console. While the messages generated at boot-time appear on the console, they may also be seen on a terminal after the boot succeeds by typing the command: dmesg. If the boot fails this will not be of any use, so you may want to have a terminal display the messages during the booting.
It's possible to patch the Linux kernel to do this and recompile it. This will send a terminal the messages which are normally sent only to the console. It doesn't fully make the terminal into a console since one can't remap the keyboard nor change colors like most consoles can. The Linux Journal in April 1997 had an article on this. To patch the Linux kernel add a couple of #defines at the start of src/linux/drivers/char/console.c:
<item> #define CONFIG_SERIAL_ECHO <item> #define SERIAL_ECHO_PORT 0x2f8 /* Serial port address */
If you currently use the console to select which operating system to boot (using LILO), but would like to do this from a terminal, then you need to add a line to the /etc/lilo.conf file. See the manual page for lilo.conf and search for "serial=".