There are two ways to interact with BeOS. The first is apparent from the moment the system boots: Take the mouse and click on the pretty pictures. This allows the beginner to use the system immediately. For advanced users, however, the point-and-click routine becomes tedious, resulting in such "impure" features as keyboard accelerators.

The second way to interact with BeOS takes the keyboard accelerator concept to the logical conclusion: Dispense with the mouse, and use the keyboard only. This happens when you start the Be app called Terminal. It reads a line of text >from the keyboard, and interprets it according to well-defined rules.

Real-world users rely on a mix of these two approaches: The painting program needs a file name (which you type), while Terminal users can construct new command lines by cutting-and-pasting.

The Posix-compliance of BeOS is not merely a crutch to allow developers to port archaic programs. The persistence of UNIX-like systems, and the accompanying terminal emulators, shows the attraction and power of expressing your computational desires in a symbolic way. From a contributor to the "fortune" command:

GUI fanatics are free to send me a picture of this quotation!

Terminal is mistakenly considered a monolithic application that reads and processes commands. It is actually one of several modular components, which can be recombined in useful ways. Of chief interest is the "shell", to use the UNIX terminology. The shell is a program which reads a command line, parses it, and then executes another program to do the work. The /bin directory contains many useful commands, familiar to UNIX users. The shell shipped by Be is "bash", but is easily replaced at the user's whimsy.

Here are some BeOS configurations:

bash <-> pty <-> Terminal <-> AppServer <-> keyboard/screen

bc <-> pty <-> Terminal <-> AppServer <-> keyboard/screen

bash <-> pty <-> NetServer <-> network card

bash <-> serial driver <-> serial port

The first configuration applies when you double-click the Terminal icon, or type "Terminal" to the shell. The second applies if you type "Terminal /bin/bc", which starts the "bc" desk calculator instead of a shell. A command other than "bc" may be specified, of course. The third applies if you connect to your BeOS machine from the network: You must enable "telnet" service in Network preferences. The last configuration will be supported in the next release, and permits remote logins from a serial device, such as a modem.

The pseudo-tty driver, "pty", serves the same purpose as that in the UNIX world. Both "pty" and the serial driver provide uniform services in the area of low-level character handling. This handling is programmable using the "termios" family of functions, described in any Posix manual. From the shell, use the "stty" command: Type "stty—help" for help.

Note that the shell is usable in a non-interactive setting, reading commands from a file. This scripting ability is enhanced by its built-in programming primitives. Look at /system/boot/Bootscript for an example. A "shell command file" can be started from the Tracker just like any Be app. The "bash" manual gives exhaustive details about shell programming.

UNIX pioneered the notion of describing the characteristics and abilities of standalone terminals, a.k.a. glass TTYs. There was a plentiful assortment in the 70s and 80s, with differences that could best be described as gratuitous. The publicly assembled file, stored in /etc/termcap, allowed programs like text editors and games to move the cursor all over the screen, without knowing the particular brand of incompatible tty being used.

This file is shipped with the BeOS, and comes in handy when you want to run "vi" or "emacs" locally in a Terminal window. It is also needed if you log into a BeOS system from Solaris, or from that VAX VMS system with the TeleVideo.

The BeOS will also ship with "ncurses", a powerful library built on termcap, and used by many terminal-oriented programs. This is based on the "curses" library of BSD UNIX.

In the 90s, most terminal manufacturers have departed the business (or this world). The market remains for terminal emulators, such as ProComm, Kermit, xterm of X Windows, and all UNIX workstation consoles. Be's Terminal app falls in this category. All follow the loosely-defined ANSI X3.64 standard.

The character set used by Terminal is 8-bit. The appearance is determined by the font selected by the user—usually some approximation of ASCII, or ISO Latin1 for Europeans. The BeOS supports 16-bit Unicode, but the design impact on Terminal is undecided. The BeOS has selected the Unicode byte encoding called UTF-8. The ASCII character set is 7-bit, and maps one-to-one onto UTF-8. However, bytes in the range 0x80–0xFF start a multi-byte UTF representation of a Unicode character. This conflicts with 8-bit character sets, like Latin1.

This is only one example of the conflict between Terminal's mandate to faithfully emulate the past, and the desire to keep one foot in the present.

The ANSI standard defines some aspects of terminal behavior, such as the effects of various escape sequences. The standard is too vague to implement a working emulator; the successor standard, ISO 6429, is similarly deficient. For example, cursor behavior at end-of-line is undefined: A program cannot know whether to expect line truncation, line wrap, or a flashing blue screen.

Instead, writers of "ANSI" emulation must rely on existing TTYs, such as the old VT family from DEC, or other emulators. This is much better than the free-for-all in past decades, but is still aggravating for users.

The problem is not solved by termcap. Observe that you can use "telnet" in Terminal to log into a remote system. /etc/termcap on the BeOS is not used in this case. If the other system has termcap support, you can transfer the "ANSI BeBox Terminal" entry to the remote system. Otherwise, you must cross your fingers and claim to be "vt100", "linux", "xterm", or some such.

The best approach would be for Terminal to emulate several well-known commercial products, allowing the user to make whatever claim that works for the remote system. Needless to say, this is an arduous task.

Further complications arise in the keyboard department. The existing standards say nothing about keyboard layout, or the characters and escape sequences to be sent by those keys. The current situation is one of bewildering variety. Many emulators have programmable keys, but this only places the burden on the user.

The current goal is to have Terminal emulate all useful aspects of the DEC VT220. A large fraction of these capabilities have already been implemented.

Like every good Be app, Terminal provides access to the system-wide clipboard, allowing text to be copied and pasted. The usual menu method and keyboard accelerations are employed.

For users with a 2-button mouse, the rightmost button will paste text from the clipboard. As a further shortcut, if the window contains selected text, this text, rather than the clipboard, will be pasted.

Since the cursor can be moved anywhere on the screen, and overwrite any portion, the definition of the "correct text" to copy and paste is sometimes unknown. This is a problem for all terminals and emulators with text retrieval ability. The usual route taken is to copy the text as it appears on the screen, but that means tabs are replaced by spaces. It also creates trouble for multi-line copies, where text may have been wrapped.

The appearance of characters can be embellished by the use of "attributes". Terminal, for example, allows underlining, reverse video, bold, background color, and foreground color. These attributes can be combined freely, using the appropriate escape sequences. The permitted colors are white, black, red, green, blue, yellow, cyan and magenta: watch out for unreadable combinations!

When you start a new Terminal, the "Be" logo is generated using various attributes: underline, bold, and color. Inspecting /etc/profile shows the trick. The following command can be typed to the shell verbatim:

echo -e "\nWelcome to the \033[1;4;34mB\033[1;4;31me\033[m shell.\n"

The [-e] flag to the "echo" command allows binary bytes to be represented with printable strings. So "\n" means ASCII Line Feed (octal 012), and "\033" means ASCII Escape (octal 033). To enable the bold attribute, try

echo -e "\033[1m"

Then also enable a blue foreground with

echo -e "\033[34m"

Disable everything with

echo -e "\033[m"

Here is the complete list currently supported by Terminal:

1  bold
4  underline
7  reverse video
30 black foreground
31 red foreground
32 green foreground
33 yellow foreground
34 blue foreground
35 magenta foreground
36 cyan foreground
37 white foreground
40 black background
41 red background
42 green background
43 yellow background
44 blue background
45 magenta background
46 cyan background
47 white background

Observe that no programming library like "curses", or any file like /etc/termcap, is needed to use escape sequences. You can use these embellishments in shell command files, or in C programs with printf(). In fact, all escape sequences are this simple to invoke.

For those interested in other escape sequences supported by Terminal, and terminals in general, the first file to peruse is /etc/termcap. A man page for "termcap" is needed to parse the entries, but a useful description of ANSI-style escape sequences is included near the end of the file.

Another excellent Internet resource is:

This contains a veritable trove of technical info, historical trivia, selected discussions from Internet news groups, and test programs.

Last, and least, you can order ISO 6429 from http://www.ansi.org/ for $130 or so. Save your money.