terminfo(4)

Boolean Capabilities

A boolean capability is true if its Capname is present in the entry, and false if its Capname is not present in the entry.

The "@" character following a Capname is used to explicitly declare that a boolean capability is false, in situations described in the Similar Terminals subsection of the Insert/Delete Line section below.

Numeric Capabilities

Numeric capabilities are followed by the character "#" and then a positive integer value. The example assigns the value 80 to the cols numeric capability by coding:

Values for numeric capabilities may be specified in decimal, octal or hexadecimal, using normal C-language conventions.

String Capabilities

String-valued capabilities such as el (clear to end of line sequence) are listed by the Capname, an "=", and a string ended by the next occurrence of a comma.

A delay in milliseconds may appear anywhere in such a capability, preceded by "$" and enclosed in angle brackets, as in el=\EK$<3>. The Curses implementation achieves delays by outputting to the terminal an appropriate number of system-defined padding characters. The tputs() function provides delays when used to send such a capability to the terminal.

The delay can be any of the following: a number; a number followed by an asterisk, such as 5*; a number followed by a slash, such as 5/; or a number followed by both, such as 5*/.

The following notation is valid in terminfo source files for specifying special characters:

(See the "X/Open System Interface Definitions, Issue 4, Version 2" specification, "General Terminal Interface".)

Commented-Out Capabilities

Sometimes individual capabilities must be commented out. To do this, put a period before the capability name. For example, see the second ind in the example in the Sample Entry section above. Note that capabilities are defined in a left-to-right order and, therefore, a prior definition will override a later definition.

Basic Capabilities

The number of columns on each line for the device is given by the cols numeric capability. If the device has a screen, then the number of lines on the screen is given by the lines capability. If the device wraps around to the beginning of the next line when it reaches the right margin, then it should have the am capability. If the terminal can clear its screen, leaving the cursor in the home position, then this is given by the clear string capability. If the terminal overstrikes (rather than clearing a position when a character is struck over) then it should have the os capability. If the device is a printing terminal, with no soft copy unit, specify both hc and os. If there is a way to move the cursor to the left edge of the current row, specify this as cr. (Normally this will be carriage return, control-M.) If there is a way to produce an audible signal (such as a bell or a beep), specify it as bel. If, like most devices, the device uses the XON/XOFF flow-control protocol, specify xon.

If there is a way to move the cursor one position to the left (such as backspace), that capability should be given as cub1. Similarly, sequences to move to the right, up, and down should be given as cuf1, cuu1, and cud1, respectively. These local cursor motions must not alter the text they pass over; for example, you would not normally use "cuf1=\s" because the space would erase the character moved over.

A very important point here is that the local cursor motions encoded in terminfo are undefined at the left and top edges of a screen terminal. Programs should never attempt to backspace around the left edge, unless bw is specified, and should never attempt to go up locally off the top. To scroll text up, a program goes to the bottom left corner of the screen and sends the ind (index) string. To scroll text down, a program goes to the top left corner of the screen and sends the ri (reverse index) string. The strings ind and ri are undefined when not on their respective corners of the screen.

Parameterized versions of the scrolling sequences are indn and rin. These versions have the same semantics as ind and ri, except that they take one argument and scroll the number of lines specified by that argument. They are also undefined except at the appropriate edge of the screen.

The am capability tells whether the cursor sticks at the right edge of the screen when text is output, but this does not necessarily apply to a cuf1 from the last column. Backward motion from the left edge of the screen is possible only when bw is specified. In this case, cub1 will move to the right edge of the previous row. If bw is not given, the effect is undefined. This is useful for drawing a box around the edge of the screen, for example. If the device has switch-selectable automatic margins, am should be specified in the terminfo source file. In this case, initialization strings should turn on this option, if possible. If the device has a command that moves to the first column of the next line, that command can be given as nel (newline). It does not matter if the command clears the remainder of the current line, so if the device has no cr and lf it may still be possible to craft a working nel out of one or both of them.

These capabilities suffice to describe hardcopy and screen terminals. Thus the AT&T 5320 hardcopy terminal is described as follows:

while the Lear Siegler ADM-3 is described as

Parameterized Strings

Cursor addressing and other strings requiring arguments are described by a argumentized string capability with escapes in a form (%x) comparable to printf() (see printf(1)). For example, to address the cursor, the cup capability is given, using two arguments: the row and column to address to. (Rows and columns are numbered from zero and refer to the physical screen visible to the user, not to any unseen memory.) If the terminal has memory relative cursor addressing, that can be indicated by mrcup.

The argument mechanism uses a stack and special "%" codes to manipulate the stack in the manner of Reverse Polish Notation (postfix). Typically a sequence pushes one of the arguments onto the stack and then prints it in some format. Often more complex operations are necessary. Operations are in postfix form with the operands in the usual order. That is, to subtract 5 from the first argument, one would use %p1%{5}%-.

The "%" encodings have the following meanings:

If the "-" flag is used with "%[doxXs]", then a colon must be placed between the "%" and the "-" to differentiate the flag from the binary "%-" operator. For example: "%:-16.16s".

Consider the Hewlett-Packard 2645, which, to get to row 3 and column 12, needs to be sent \E&a12c03Y padded for 6 milliseconds. Note that the order of the rows and columns is inverted here, and that the row and column are zero-padded as two digits. Thus, its cup capability is:

The Micro-Term ACT-IV needs the current row and column sent preceded by a ^T, with the row and column simply encoded in binary:

Devices that use "%c" need to be able to backspace the cursor (cub1), and to move the cursor up one line on the screen (cuu1). This is necessary because it is not always safe to transmit \n, ^D, and \r, as the system may change or discard them. (The library functions dealing with terminfo set tty modes so that tabs are never expanded, so \t is safe to send. This turns out to be essential for the Ann Arbor 4080.)

A final example is the LSI ADM-3a, which uses row and column offset by a blank character, thus:

After sending "\E=", this pushes the first argument, pushes the ASCII decimal value for a space (32), adds them (pushing the sum on the stack in place of the two previous values), and outputs that value as a character. Then the same is done for the second argument. More complex arithmetic is possible using the stack.

Cursor Motions

If the terminal has a fast way to home the cursor (to very upper left corner of screen) then this can be given as home; similarly a fast way of getting to the lower left-hand corner can be given as ll; this may involve going up with cuu1 from the home position, but a program should never do this itself (unless ll does) because it can make no assumption about the effect of moving up from the home position. Note that the home position is the same as addressing to (0,0): to the top left corner of the screen, not of memory. (Thus, the \EH sequence on Hewlett-Packard terminals cannot be used for home without losing some of the other features on the terminal.)

If the device has row or column absolute-cursor addressing, these can be given as single argument capabilities hpa (horizontal position absolute) and vpa (vertical position absolute). Sometimes these are shorter than the more general two-argument sequence (as with the Hewlett-Packard 2645) and can be used in preference to cup. If there are argumentized local motions (such as "move n spaces to the right"), these can be given as cud, cub, cuf, and cuu with a single argument indicating how many spaces to move. These are primarily useful if the device does not have cup, such as the Tektronix 4025.

If the device needs to be in a special mode when running a program that uses these capabilities, the codes to enter and exit this mode can be given as smcup and rmcup. This arises, for example, from terminals, such as the Concept, with more than one page of memory. If the device has only memory relative cursor addressing and not screen relative cursor addressing, a one screen-sized window must be fixed into the device for cursor addressing to work properly. This is also used for the Tektronix 4025, where smcup sets the command character to be the one used by terminfo. If the rmcup sequence will not restore the screen after an smcup sequence is output (to the state prior to outputting smcup), specify nrrmc.

Area Clears

If the terminal can clear from the current position to the end of the line, leaving the cursor where it is, this should be given as el. If the terminal can clear from the beginning of the line to the current position inclusive, leaving the cursor where it is, this should be given as el1. If the terminal can clear from the current position to the end of the display, then this should be given as ed. ed is only defined from the first column of a line. (Thus, it can be simulated by a request to delete a large number of lines, if a true ed is not available.)

Insert/Delete Character

There are two basic kinds of intelligent terminals with respect to insert/delete character operations which can be described using terminfo. The most common insert/delete character operations affect only the characters on the current line and shift characters off the end of the line rigidly. Other terminals, such as the Concept 100 and the Perkin-Elmer Owl, make a distinction between typed and untyped blanks on the screen, shifting upon an insert or delete only to an untyped blank on the screen which is either eliminated, or expanded to two untyped blanks. You can determine the kind of terminal you have by clearing the screen and then typing text separated by cursor motions. Type "abc def" using local cursor motions (not spaces) between the abc and the def. Then position the cursor before the abc and put the terminal in insert mode. If typing characters causes the rest of the line to shift rigidly and characters to fall off the end, then your terminal does not distinguish between blanks and untyped positions. If the abc shifts over to the def which then move together around the end of the current line and onto the next as you insert, you have the second type of terminal, and should give the capability in, which stands for "insert null". While these are two logically separate attributes (one line versus multiline insert mode, and special treatment of untyped spaces) we have seen no terminals whose insert mode cannot be described with the single attribute.

terminfo can describe both terminals that have an insert mode and terminals which send a simple sequence to open a blank position on the current line. Give as smir the sequence to get into insert mode. Give as rmir the sequence to leave insert mode. Now give as ich1 any sequence needed to be sent just before sending the character to be inserted. Most terminals with a true insert mode will not give ich1; terminals that send a sequence to open a screen position should give it here. (If your terminal has both, insert mode is usually preferable to ich1. Do not give both unless the terminal requires both to be used in combination.) If post-insert padding is needed, give this as a number of milliseconds padding in ip (a string option). Any other sequence which may need to be sent after an insert of a single character may also be given in ip. If your terminal needs both to be placed into an "insert mode" and a special code to precede each inserted character, then both smir/rmir and ich1 can be given, and both will be used. The ich capability, with one argument, n, will insert n blanks.

If padding is necessary between characters typed while not in insert mode, give this as a number of milliseconds padding in rmp.

It is occasionally necessary to move around while in insert mode to delete characters on the same line (for example, if there is a tab after the insertion position). If your terminal allows motion while in insert mode you can give the capability mir to speed up inserting in this case. Omitting mir will affect only speed. Some terminals (notably Datamedia) must not have mir because of the way their insert mode works.

Finally, you can specify dch1 to delete a single character, dch with one argument, n, to delete n characters, and delete mode by giving smdc and rmdc to enter and exit delete mode (any mode the terminal needs to be placed in for dch1 to work).

A command to erase n characters (equivalent to outputting n blanks without moving the cursor) can be given as ech with one argument.

Highlighting, Underlining, and Visible Bells

Your device may have one or more kinds of display attributes that allow you to highlight selected characters when they appear on the screen. The following display modes (shown with the names by which they are set) may be available:

sgr0 should be used to turn off all video enhancement capabilities. It should always be specified because it represents the only way to turn off some capabilities, such as dim or blink.

Choose one display method as standout mode and use it to highlight error messages and other text to which you want to draw attention. Choose a form of display that provides strong contrast but that is easy on the eyes. (We recommend reverse-video plus half-bright or reverse-video alone.) The sequences to enter and exit standout mode are given as smso and rmso, respectively. If the code to change into or out of standout mode leaves one or even two blank spaces on the screen, as the TVI 912 and Teleray 1061 do, then xmc should be given to tell how many spaces are left.

Sequences to begin underlining and end underlining can be specified as smul and rmul, respectively. If the device has a sequence to underline the current character and to move the cursor one space to the right (such as the Micro-Term MIME), this sequence can be specified as uc.

Terminals with the "magic cookie" glitch (xmc) deposit special "cookies" when they receive mode-setting sequences, which affect the display algorithm rather than having extra bits for each character. Some terminals, such as the Hewlett-Packard 2621, automatically leave standout mode when they move to a new line or the cursor is addressed. Programs using standout mode should exit standout mode before moving the cursor or sending a newline, unless the msgr capability, asserting that it is safe to move in standout mode, is present.

If the terminal has a way of flashing the screen to indicate an error quietly (a bell replacement), then this can be given as flash; it must not move the cursor. A good flash can be done by changing the screen into reverse video, pad for 200 ms, then return the screen to normal video.

If the cursor needs to be made more visible than normal when it is not on the bottom line (to make, for example, a nonblinking underline into an easier to find block or blinking underline) give this sequence as cvvis. The boolean chts should also be given. If there is a way to make the cursor completely invisible, give that as civis. The capability cnorm should be given, which undoes the effects of either of these modes.

If your terminal generates underlined characters by using the underline character (with no special sequences needed) even though it does not otherwise overstrike characters, then specify the capability ul. For devices on which a character overstriking another leaves both characters on the screen, specify the capability os. If overstrikes are erasable with a blank, then this should be indicated by specifying eo.

If there is a sequence to set arbitrary combinations of modes, this should be given as sgr (set attributes), taking nine arguments. Each argument is either 0 or nonzero, as the corresponding attribute is on or off. The nine arguments are, in order: standout, underline, reverse, blink, dim, bold, blank, protect, alternate character set. Not all modes need to be supported by sgr; only those for which corresponding separate attribute commands exist should be supported. For example, let's assume that the terminal in question needs the following escape sequences to turn on various modes.

Note that each escape sequence requires a 0 to turn off other modes before turning on its own mode. Also note that, as suggested above, standout is set up to be the combination of reverse and dim. Also, because this terminal has no bold mode, bold is set up as the combination of reverse and underline. In addition, to allow combinations, such as underline+blink, the sequence to use would be \E[0;3;5m. The terminal doesn't have protect mode, either, but that cannot be simulated in any way, so p8 is ignored. The altcharset mode is different in that it is either ^O or ^N, depending on whether it is off or on. If all modes were to be turned on, the sequence would be:

Now look at when different sequences are output. For example, ;3 is output when either p2 or p6 is true, that is, if either underline or bold modes are turned on. Writing out the above sequences, along with their dependencies, gives the following:

Putting this all together into the sgr sequence gives:

Remember that sgr and sgr0 must always be specified.

Keypad

If the device has a keypad that transmits sequences when the keys are pressed, this information can also be specified. Note that it is not possible to handle devices where the keypad only works in local (this applies, for example, to the unshifted Hewlett-Packard 2621 keys). If the keypad can be set to transmit or not transmit, specify these sequences as smkx and rmkx. Otherwise the keypad is assumed to always transmit.

The sequences sent by the left arrow, right arrow, up arrow, down arrow, and home keys can be given as kcub1, kcuf1, kcuu1, kcud1 and khome, respectively. If there are function keys such as f0, f1, ..., f63, the sequences they send can be specified as kf0, kf1, ..., kf63. If the first 11 keys have labels other than the default f0 through f10, the labels can be given as lf0, lf1, ..., lf10.

The codes transmitted by certain other special keys can be given: kll (home down), kbs (backspace), ktbc (clear all tabs), kctab (clear the tab stop in this column), kclr (clear screen or erase key), kdch1 (delete character), kdl1 (delete line), krmir (exit insert mode), kel (clear to end of line), ked (clear to end of screen), kich1 (insert character or enter insert mode), kil1 (insert line), knp (next page), kpp (previous page), kind (scroll forward/down), kri (scroll backward/up), khts (set a tab stop in this column). In addition, if the keypad has a 3 by 3 array of keys including the four arrow keys, the other five keys can be given as ka1, ka3, kb2, kc1, and kc3. These keys are useful when the effects of a 3 by 3 directional pad are needed. Further keys are defined above in the capabilities list.

Strings to program function keys can be specified as pfkey, pfloc, and pfx. A string to program screen labels should be specified as pln. Each of these strings takes two arguments: a function key identifier and a string to program it with. pfkey causes pressing the given key to be the same as the user typing the given string; pfloc causes the string to be executed by the terminal in local mode; and pfx causes the string to be transmitted to the computer. The capabilities nlab, lw and lh define the number of programmable screen labels and their width and height. If there are commands to turn the labels on and off, give them in smln and rmln. smln is normally output after one or more pln sequences to make sure that the change becomes visible.

Tabs and Initialization

If the device has hardware tabs, the command to advance to the next tab stop can be given as ht (usually control-I). A "backtab" command that moves leftward to the next tab stop can be given as cbt. By convention, if tty modes show that tabs are being expanded by the computer rather than being sent to the device, programs should not use ht or cbt (even if they are present) because the user might not have the tab stops properly set. If the device has hardware tabs that are initially set every n spaces when the device is powered up, the numeric argument it is given, showing the number of spaces the tabs are set to. This is normally used by tput init to determine whether to set the mode for hardware tab expansion and whether to set the tab stops. If the device has tab stops that can be saved in nonvolatile memory, the terminfo description can assume that they are properly set. If there are commands to set and clear tab stops, they can be given as tbc (clear all tab stops) and hts (set a tab stop in the current column of every row).

Other capabilities include: is1, is2, and is3, initialization strings for the device; iprog, the path name of a program to be run to initialize the device; and if, the name of a file containing long initialization strings. These strings are expected to set the device into modes consistent with the rest of the terminfo description. They must be sent to the device each time the user logs in and be output in the following order: run the program iprog; output is1; output is2; set the margins using mgc, smgl and smgr; set the tabs using tbc and hts; print the file if; and finally output is3. This is usually done using the init option of tput.

Most initialization is done with is2. Special device modes can be set up without duplicating strings by putting the common sequences in is2 and special cases in is1 and is3. Sequences that do a reset from a totally unknown state can be given as rs1, rs2, rf, and rs3, analogous to is1, is2, is3, and if. (The method using files, if and rf, is used for a few terminals; however, the recommended method is to use the initialization and reset strings.) These strings are output by tput reset, which is used when the terminal gets into a wedged state. Commands are normally placed in rs1, rs2, rs3, and rf only if they produce annoying effects on the screen and are not necessary when logging in. For example, the command to set a terminal into 80-column mode would normally be part of is2, but on some terminals it causes an annoying glitch on the screen and is not normally needed because the terminal is usually already in 80-column mode.

If a more complex sequence is needed to set the tabs than can be described by using tbc and hts, the sequence can be placed in is2 or if.

Any margin can be cleared with mgc. (For instructions on how to specify commands to set and clear margins, see the Margins subsection of the Capabilities That Cause Movement section below.

Delays

Certain capabilities control padding in the tty driver. These are primarily needed by hard-copy terminals, and are used by tput init to set tty modes appropriately (see tput(1)). Delays embedded in the capabilities cr, ind, cub1, ff, and tab can be used to set the appropriate delay bits to be set in the tty driver. If pb (padding baud rate) is given, these values can be ignored at baud rates below the value of pb.

Status Lines

If the terminal has an extra "status line" that is not normally used by software, this fact can be indicated. If the status line is viewed as an extra line below the bottom line, into which one can cursor-address normally (such as the Heathkit H19's 25th line, or the 24th line of a VT100 which is set to a 23-line scrolling region), the capability hs should be given. Special strings that go to a given column of the status line and return from the status line can be given as tsl and fsl. (fsl must leave the cursor position in the same place it was before tsl. If necessary, the sc and rc strings can be included in tsl and fsl to get this effect.) The capability tsl takes one argument, which is the column number of the status line the cursor is to be moved to.

If escape sequences and other special commands, such as tab, work while in the status line, the flag eslok can be given. A string which turns off the status line (or otherwise erases its contents) should be given as dsl. If the terminal has commands to save and restore the position of the cursor, give them as sc and rc. The status line is normally assumed to be the same width as the rest of the screen (that is, cols). If the status line is a different width (possibly because the terminal does not allow an entire line to be loaded) the width, in columns, can be indicated with the numeric argument wsl.

Line Graphics

If the device has a line drawing alternate character set, the mapping of glyph to character would be given in acsc. The definition of this string is based on the alternate character set used in the Digital VT100 terminal, extended slightly with some characters from the AT&T 4410v1 terminal.

The best way to describe a new device's line graphics set is to add a third column to the above table with the characters for the new device that produce the appropriate glyph when the device is in alternate-character-set mode. For example:

Now write down the characters left to right; for example:

In addition, terminfo lets you define multiple character sets (see the Alternate Character Sets section below).

Color Manipulation

Most color terminals belong to one of two classes of terminal:

The numeric variables colors and pairs define the number of colors and color-pairs that can be displayed on the screen at the same time. If a terminal can change the definition of a color (for example, the Tektronix 4100 and 4200 series terminals), this should be specified with ccc (can change color). To change the definition of a color (Tektronix 4200 method), use initc (initialize color). It requires four arguments: color number (ranging from 0 to colors-1) and three RGB (red, green, and blue) values or three HLS colors (Hue, Lightness, Saturation). Ranges of RGB and HLS values are terminal-dependent.

Tektronix 4100 series terminals only use HLS color notation. For such terminals (or dual-mode terminals to be operated in HLS mode) one must define a boolean variable hls; that would instruct the init_color() function (see can_change_color(3X)) to convert its RGB arguments to HLS before sending them to the terminal. The last three arguments to the initc string would then be HLS values.

If a terminal can change the definitions of colors, but uses a color notation different from RGB and HLS, a mapping to either RGB or HLS must be developed.

If the terminal supports ANSI escape sequences to set background and foreground, they should be coded as setab and setaf, respectively. If the terminal supports other escape sequences to set background and foreground, they should be coded as setb and setf, respectively. The vidputs() function (see vidattr(3X)) and the refresh functions use setab and setaf if they are defined. Each of these capabilities requires one argument: the number of the color. By convention, the first eight colors (0-7) map to, in order: black, red, green, yellow, blue, magenta, cyan, white. However, color re-mapping may occur or the underlying hardware may not support these colors. Mappings for any additional colors supported by the device (that is, to numbers greater than 7) are at the discretion of the terminfo entry writer.

To initialize a color-pair (HP method), use initp (initialize pair). It requires seven arguments: the number of a color-pair (range=0 to pairs-1), and six RGB values: three for the foreground followed by three for the background. (Each of these groups of three should be in the order RGB.) When initc or initp are used, RGB or HLS arguments should be in the order "red, green, blue" or "hue, lightness, saturation"), respectively. To make a color-pair current, use scp (set color-pair). It takes one argument, the number of a color-pair.

Some terminals (for example, most color terminal emulators for PCs) erase areas of the screen with current background color. In such cases, bce (background color erase) should be defined. The variable op (original pair) contains a sequence for setting the foreground and the background colors to what they were at the terminal start-up time. Similarly, oc (original colors) contains a control sequence for setting all colors (for the Tektronix method) or color-pairs (for the HP method) to the values they had at the terminal start-up time.

Some color terminals substitute color for video attributes. Such video attributes should not be combined with colors. Information about these video attributes should be packed into the ncv (no color video) variable. There is a one-to-one correspondence between the nine least significant bits of that variable and the video attributes. The following table depicts this correspondence.

When a particular video attribute should not be used with colors, set the corresponding ncv bit to 1; otherwise set it to 0. To determine the information to pack into the ncv variable, add the decimal values corresponding to those attributes that cannot coexist with colors. For example, if the terminal uses colors to simulate reverse video (bit number 2 and decimal value 4) and bold (bit number 5 and decimal value 32), the resulting value for ncv will be 36 (4 + 32).

Miscellaneous

If the terminal requires other than a null (zero) character as a pad, then this can be given as pad. Only the first character of the pad string is used. If the terminal does not have a pad character, specify npc.

If the terminal can move up or down half a line, this can be indicated with hu (half-line up) and hd (half-line down). This is primarily useful for superscripts and subscripts on hardcopy terminals. If a hardcopy terminal can eject to the next page (form feed), give this as ff (usually control-L).

If there is a command to repeat a given character a given number of times (to save time transmitting a large number of identical characters) this can be indicated with the argumentized string rep. The first argument is the character to be repeated and the second is the number of times to repeat it. Thus, tparm(repeat_char, 'x', 10) is the same as xxxxxxxxxx.

If the terminal has a settable command character, such as the Tektronix 4025, this can be indicated with cmdch. A prototype command character is chosen which is used in all capabilities. This character is given in the cmdch capability to identify it. The following convention is supported on some systems: If the environment variable CC exists, all occurrences of the prototype character are replaced with the character in CC.

Terminal descriptions that do not represent a specific kind of known terminal, such as switch, dialup, patch, and network, should include the gn (generic) capability so that programs can complain that they do not know how to talk to the terminal. (This capability does not apply to virtual terminal descriptions for which the escape sequences are known.) If the terminal is one of those supported by the virtual terminal protocol, the terminal number can be given as vt. A line-turn-around sequence to be transmitted before doing reads should be specified in rfi.

If the device uses XON/XOFF handshaking for flow control, give xon. Padding information should still be included so that functions can make better decisions about costs, but actual pad characters will not be transmitted. Sequences to turn on and off XON/XOFF handshaking may be given in smxon and rmxon. If the characters used for handshaking are not ^S and ^Q, they may be specified with xonc and xoffc.

If the terminal has a "meta key" which acts as a shift key, setting the 8th bit of any character transmitted, this fact can be indicated with km. Otherwise, software will assume that the 8th bit is parity and it will usually be cleared. If strings exist to turn this "meta mode" on and off, they can be given as smm and rmm.

If the terminal has more lines of memory than will fit on the screen at once, the number of lines of memory can be indicated with lm. A value of lm#0 indicates that the number of lines is not fixed, but that there is still more memory than fits on the screen.

Media copy strings which control an auxiliary printer connected to the terminal can be given as:

When the printer is on, all text sent to the terminal will be sent to the printer. A variation, mc5p, takes one argument, and leaves the printer on for as many characters as the value of the argument, then turns the printer off. The argument should not exceed 255. If the text is not displayed on the terminal screen when the printer is on, specify mc5i (silent printer). All text, including mc4, is transparently passed to the printer while an mc5p is in effect.

Special Cases

The working model used by terminfo fits most terminals reasonably well. However, some terminals do not completely match that model, requiring special support by terminfo. These are not meant to be construed as deficiencies in the terminals; they are just differences between the working model and the actual hardware. They may be unusual devices or, for some reason, do not have all the features of the terminfo model implemented.

Terminals that cannot display tilde (~) characters, such as certain Hazeltine terminals, should indicate hz.

Terminals that ignore a line feed immediately after an am wrap, such as the Concept 100, should indicate xenl. Those terminals whose cursor remains on the right-most column until another character has been received, rather than wrapping immediately upon receiving the right-most character, such as the VT100, should also indicate xenl.

If el is required to get rid of standout (instead of writing normal text on top of it), xhp should be given.

Those Teleray terminals whose tabs turn all characters moved over to blanks, should indicate xt (destructive tabs). This capability is also taken to mean that it is not possible to position the cursor on top of a "magic cookie". Therefore, to erase standout mode, it is necessary, instead, to use delete and insert line.

For Beehive Superbee terminals that do not transmit the escape or control-C characters, specify xsb, indicating that the f1 key is to be used for escape and the f2 key for control-C.

Similar Terminals

If there are two similar terminals, one can be defined as being just like the other with certain exceptions. The string capability use can be given with the name of the similar terminal. The capabilities given before use override those in the terminal type invoked by use. A capability can be canceled by placing capability-name@ prior to the appearance of the string capability use. For example, the entry:

defines an AT&T 04424 terminal that does not have the rev, sgr, and smul capabilities, and hence cannot do highlighting. This is useful for different modes for a terminal, or for different user preferences. More than one use capability may be given.

Rounding Values

Because argumentized string capabilities work only with integer values, terminfo designers should create strings that expect numeric values that have been rounded. Application designers should note this and should always round values to the nearest integer before using them with a argumentized string capability.

Printer Resolution

A printer's resolution is defined to be the smallest spacing of characters it can achieve. In general, the horizontal and vertical resolutions are independent. Thus the vertical resolution of a printer can be determined by measuring the smallest achievable distance between consecutive printing baselines, while the horizontal resolution can be determined by measuring the smallest achievable distance between the leftmost edges of consecutive printed, identical, characters.

All printers are assumed to be capable of printing with a uniform horizontal and vertical resolution. The view of printing that terminfo currently presents is one of printing inside a uniform matrix: All characters are printed at fixed positions relative to each "cell" in the matrix; furthermore, each cell has the same size given by the smallest horizontal and vertical step sizes dictated by the resolution. (The cell size can be changed as will be seen later.)

Many printers are capable of "proportional printing", where the horizontal spacing depends on the size of the character last printed. terminfo does not make use of this capability, although it does provide enough capability definitions to allow an application to simulate proportional printing.

A printer must not only be able to print characters as close together as the horizontal and vertical resolutions suggest, but also of "moving" to a position an integral multiple of the smallest distance away from a previous position. Thus printed characters can be spaced apart a distance that is an integral multiple of the smallest distance, up to the length or width of a single page.

Some printers can have different resolutions depending on different "modes". In "normal mode", the existing terminfo capabilities are assumed to work on columns and lines, just like a video terminal. Thus the old lines capability would give the length of a page in lines, and the cols capability would give the width of a page in columns. In "micro mode," many terminfo capabilities work on increments of lines and columns. With some printers the micro mode may be concomitant with normal mode, so that all the capabilities work at the same time.

Specifying Printer Resolution

The printing resolution of a printer is given in several ways. Each specifies the resolution as the number of smallest steps per distance:

When printing in normal mode, each character printed causes movement to the next column, except in special cases described later; the distance moved is the same as the per-column resolution. Some printers cause an automatic movement to the next line when a character is printed in the rightmost position; the distance moved vertically is the same as the per-line resolution. When printing in micro mode, these distances can be different, and may be zero for some printers.

Some printers are capable of printing wide characters. The distance moved when a wide character is printed in normal mode may be different from when a regular width character is printed. The distance moved when a wide character is printed in micro mode may also be different from when a regular character is printed in micro mode, but the differences are assumed to be related: If the distance moved for a regular character is the same whether in normal mode or micro mode (mcs=orc), then the distance moved for a wide character is also the same whether in normal mode or micro mode. This doesn't mean the normal character distance is necessarily the same as the wide character distance, just that the distances don't change with a change in normal to micro mode. However, if the distance moved for a regular character is different in micro mode from the distance moved in normal mode (mcs<orc), the micro mode distance is assumed to be the same for a wide character printed in micro mode, as the table below shows.

There may be control sequences to change the number of columns per inch (the character pitch) and to change the number of lines per inch (the line pitch). If these are used, the resolution of the printer changes, but the type of change depends on the printer:

The cpi and lpi string capabilities are each used with a single argument, the pitch in columns (or characters) and lines per inch, respectively. The chr and cvr string capabilities are each used with a single argument, the number of steps per column and line, respectively.

Using any of the control sequences in these strings will imply a change in some of the values of orc, orhi, orl, and orvi. Also, the distance moved when a wide character is printed, widcs, changes in relation to orc. The distance moved when a character is printed in micro mode, mcs, changes similarly, with one exception: if the distance is 0 or 1, then no change is assumed.

Programs that use cpi, lpi, chr, or cvr should recalculate the printer resolution (and should recalculate other values. See the Effect of Changing Printing Resolution section below.

Vchr, Vcpi, Vcvr, and Vlpi are the arguments used with chr, cpi, cvr, and lpi, respectively. The prime marks (') indicate the old values.

Margins

terminfo provides two strings for setting margins on terminals: one for the left and one for the right margin. Printers, however, have two additional margins, for the top and bottom margins of each page. Furthermore, some printers require not using motion strings to move the current position to a margin and then fixing the margin there, but require the specification of where a margin should be regardless of the current position. Therefore terminfo offers six additional strings for defining margins with printers.

The last four strings are used with one or more arguments that give the position of the margin or margins to set. If both of smglp and smgrp are set, each is used with a single argument, N, that gives the column number of the left and right margin, respectively. If both of smgtp and smgbp are set, each is used to set the top and bottom margin, respectively: smgtp is used with a single argument, N, the line number of the top margin; however, smgbp is used with two arguments, N and M, that give the line number of the bottom margin, the first counting from the top of the page and the second counting from the bottom. This accommodates the two styles of specifying the bottom margin in different manufacturers' printers. When coding a terminfo entry for a printer that has a settable bottom margin, only the first or second argument should be used, depending on the printer. When writing an application that uses smgbp to set the bottom margin, both arguments must be given.

If only one of smglp and smgrp is set, then it is used with two arguments, the column number of the left and right margins, in that order. Likewise, if only one of smgtp and smgbp is set, then it is used with two arguments that give the top and bottom margins, in that order, counting from the top of the page. Thus when coding a terminfo entry for a printer that requires setting both left and right or top and bottom margins simultaneously, only one of smglp and smgrp or smgtp and smgbp should be defined; the other should be left blank. When writing an application that uses these string capabilities, the pairs should be first checked to see if each in the pair is set or only one is set, and should then be used accordingly.

In counting lines or columns, line zero is the top line and column zero is the left-most column. A zero value for the second argument with smgbp means the bottom line of the page.

All margins can be cleared with mgc.

Shadows, Italics, Wide Characters, Superscripts, Subscripts

Five sets of strings describe the capabilities printers have of enhancing printed text.

If a printer requires the sshm control sequence before every character to be shadow-printed, the rshm string is left blank. Thus programs that find a control sequence in sshm but none in rshm should use the sshm control sequence before every character to be shadow-printed; otherwise, the sshm control sequence should be used once before the set of characters to be shadow-printed, followed by rshm. The same is also true of each of the sitm-ritm, swidm-rwidm, ssupm-rsupm, and ssubm-rsubm pairs.

terminfo also has a capability for printing emboldened text (bold). While shadow printing and emboldened printing are similar in that they "darken" the text, many printers produce these two types of print in slightly different ways. Generally, emboldened printing is done by overstriking the same character one or more times. Shadow printing likewise usually involves overstriking, but with a slight movement up and/or to the side so that the character is "fatter".

It is assumed that enhanced printing modes are independent modes, so that it would be possible, for instance, to shadow print italicized subscripts.

As mentioned earlier, the amount of motion automatically made after printing a wide character should be given in widcs.

If only a subset of the printable ASCII characters can be printed as superscripts or subscripts, they should be listed in supcs or subcs strings, respectively. If the ssupm or ssubm strings contain control sequences, but the corresponding supcs or subcs strings are empty, it is assumed that all printable ASCII characters are available as superscripts or subscripts.

Automatic motion made after printing a superscript or subscript is assumed to be the same as for regular characters. Thus, for example, printing any of the following three examples results in equivalent motion:

Note that the existing msgr boolean capability describes whether motion control sequences can be used while in "standout mode". This capability is extended to cover the enhanced printing modes added here. msgr should be set for those printers that accept any motion control sequences without affecting shadow, italicized, widened, superscript, or subscript printing. Conversely, if msgr is not set, a program should end these modes before attempting any motion.

Print Quality

Many dot-matrix printers can alter the dot spacing of printed text to produce near-letter-quality printing or draft-quality printing. It is important to be able to choose one or the other because the rate of printing generally decreases as the quality improves. Three strings describe these capabilities:

The capabilities are listed in decreasing levels of quality. If a printer doesn't have all three levels, the respective strings should be left blank.

Printing Rate and Buffer Size

Because there is no standard protocol that can be used to keep a program synchronized with a printer, and because modern printers can buffer data before printing it, a program generally cannot determine at any time what has been printed. Two numeric capabilities can help a program estimate what has been printed.

cps is the nominal or average rate at which the printer prints characters; if this value is not given, the rate should be estimated at one-tenth the prevailing baud rate. bufsz is the maximum number of subsequent characters buffered before the guaranteed printing of an earlier character, assuming proper flow control has been used. If this value is not given it is assumed that the printer does not buffer characters, but prints them as they are received.

As an example, if a printer has a 1000-character buffer, then sending the letter "a" followed by 1000 additional characters is guaranteed to cause the letter "a" to print. If the same printer prints at the rate of 100 characters per second, then it should take 10 seconds to print all the characters in the buffer, less if the buffer is not full. By keeping track of the characters sent to a printer, and knowing the print rate and buffer size, a program can synchronize itself with the printer.

Note that most printer manufacturers advertise the maximum print rate, not the nominal print rate. A good way to get a value to put in for cps is to generate a few pages of text, count the number of printable characters, and then see how long it takes to print the text.

Applications that use these values should recognize the variability in the print rate. Straight text, in short lines, with no embedded control sequences will probably print at close to the advertised print rate and probably faster than the rate in cps. Graphics data with a lot of control sequences, or very long lines of text, will print at well below the advertised rate and below the rate in cps. If the application is using cps to decide how long it should take a printer to print a block of text, the application should pad the estimate. If the application is using cps to decide how much text has already been printed, it should shrink the estimate. The application will thus err in favor of the user, who wants, above all, to see all the output in its correct place.

Conventions for Device Aliases

Every device must be assigned a name, such as vt100. Device names (except the long name) should be chosen using the following conventions. The name should not contain hyphens because hyphens are reserved for use when adding suffixes that indicate special modes.

These special modes may be modes that the hardware can be in, or user preferences. To assign a special mode to a particular device, append a suffix consisting of a hyphen and an indicator of the mode to the device name. For example, the -w suffix means wide mode; when specified, it allows for a width of 132 columns instead of the standard 80 columns. Therefore, if you want to use a VT100 device set to wide mode, name the device vt100-w. Use the following suffixes where possible:

Variations of Terminal Definitions

It is implementation-defined how the entries in terminfo may be created.

There is more than one way to write a terminfo entry. A minimal entry may permit applications to use Curses to operate the terminal. If the entry is enhanced to describe more of the terminal's capabilities, applications can use Curses to invoke those features, and can take advantages of optimizations within Curses and thus operate more efficiently. For most terminals, an optimal terminfo entry has already been written.