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The Termcap Library

2.3 Terminal Type Name Conventions

There are conventions for choosing names of terminal types. For one thing, all letters should be in lower case. The terminal type for a terminal in its most usual or most fundamental mode of operation should not have a hyphen in it.

If the same terminal has other modes of operation which require different terminal descriptions, these variant descriptions are given names made by adding suffixes with hyphens. Such alternate descriptions are used for two reasons:

• When the terminal has a switch that changes its behavior. Since the computer cannot tell how the switch is set, the user must tell the computer by choosing the appropriate terminal type name.

  For example, the VT-100 has a setup flag that controls whether the cursor wraps at the right margin. If this flag is set to "wrap", you must use the terminal type `vt100-am'. Otherwise you must use `vt100-nam'. Plain `vt100' is defined as a synonym for either `vt100-am' or `vt100-nam' depending on the preferences of the local site.

  The standard suffix `-am' stands for "automatic margins".

• To give the user a choice in how to use the terminal. This is done when the terminal has a switch that the computer normally controls.

  For example, the Ann Arbor Ambassador can be configured with many screen sizes ranging from 20 to 60 lines. Fewer lines make bigger characters but more lines let you see more of what you are editing. As a result, users have different preferences. Therefore, termcap provides terminal types for many screen sizes. If you choose type `aaa-30', the terminal will be configured to use 30 lines; if you choose `aaa-48', 48 lines will be used, and so on.

Here is a list of standard suffixes and their conventional meanings:

`-w'

Short for "wide". This is a mode that gives the terminal more columns than usual. This is normally a user option.

`-am'

"Automatic margins". This is an alternate description for use when the terminal's margin-wrap switch is on; it contains the `am' flag. The implication is that normally the switch is off and the usual description for the terminal says that the switch is off.

`-nam'

"No automatic margins". The opposite of `-am', this names an alternative description which lacks the `am' flag. This implies that the terminal is normally operated with the margin-wrap switch turned on, and the normal description of the terminal says so.

`-na'

"No arrows". This terminal description initializes the terminal to keep its arrow keys in local mode. This is a user option.

`-rv'

"Reverse video". This terminal description causes text output for normal video to appear as reverse, and text output for reverse video to come out as normal. Often this description differs from the usual one by interchanging the two strings which turn reverse video on and off.

This is a user option; you can choose either the "reverse video" variant terminal type or the normal terminal type, and termcap will obey.

`-s'

"Status". Says to enable use of a status line which ordinary output does not touch (see section 3.18 Status Line).

Some terminals have a special line that is used only as a status line. For these terminals, there is no need for an `-s' variant; the status line commands should be defined by default. On other terminals, enabling a status line means removing one screen line from ordinary use and reducing the effective screen height. For these terminals, the user can choose the `-s' variant type to request use of a status line.

`-nlines'

Says to operate with nlines lines on the screen, for terminals such as the Ambassador which provide this as an option. Normally this is a user option; by choosing the terminal type, you control how many lines termcap will use.

`-npagesp'

Says that the terminal has npages pages worth of screen memory, for terminals where this is a hardware option.

`-unk'

Says that description is not for direct use, but only for reference in `tc' capabilities. Such a description is a kind of subroutine, because it describes the common characteristics of several variant descriptions that would use other suffixes in place of `-unk'.