.Dd April 7, 1993
.Dt SCREEN 4
.Os FreeBSD
.Sh NAME
.Nm screen
.Nd pc display interface
.Sh DESCRIPTION
Access to the
.Ar virtual consoles
are obtained through the device files
ttyv0 - ttyvb in /dev.
Each of these files correspond to a seperate
virtual console.
All virtual console devices can be open at once, but only one is
active at a time. The active virtual console "owns" the keyboard and
display screen.
.Pp
Output to a virtual console that not currently is on the display is
saved in a buffer that holds a "screenfull" (normally 25) lines.
Any output written to
.Ar /dev/console
(the original console device) is echoed to /dev/ttyv0.
.Pp
To switch between the virtual consoles one uses the sequence
.Ar ALT+Fn
, which means hold down ALT and press one of the function keys. The
virtual console with the same number as the function key is then
selected as the current virtual console, and given exclusive use of
the keyboard and display. This switch sequence can be changed via
the keyboard mapping ioctl call (see keyboard.4)
.Pp
The number of virtual consoles is changeable in the system config
file, and need recompilation of the kernel to take any effect. The
default is 12.
The console allows entering values that are not physically
present on the keyboard via a special keysequence.
To use this facility press and hold down ALT,
then enter a decimal number from 0-255 via the numerical keypad, then
release ALT. The entered value is then used as the ASCII value for one
character. This way it is possible to enter any ASCII value.
The console understands a subset of the ANSI x3.64 character
sequences. For compatibility with the old pccons, the PC3 character
sequences is also supported.
.Pp
.Bd -literal
ANSI Seq Function Termcap entry
======= ======= ===================================== ==============
CUU E[nA move cursor up n lines up (ku)
CUD E[nB move cursor down n lines do (kd)
CUF E[nC move cursor right n characters nd (kr)
CUB E[nD move cursor left n characters bs (kl)
HPA E[n` move cursor to character position n --
HPR E[na move cursor right n characters --
VPA E[nd move cursor to line n --
VPR E[ne move cursor down n lines --
CPL E[nF move cursor to start of line, --
n lines up
CNL E[nF move cursor to start of line, --
n lines down
CUP E[y;xH Move cursor to x, y cm
HVP E[y;xf Move cursor to x, y --
CBT E[nZ Move cursor back n tab stops bt
IL E[nL Insert n blank lines al
ICH E[n@ Insert n blank characters ic
DL E[nM Delete n lines dl
DCH E[nP Delete n characters dc
ED E[nJ Erase part or all of display: cd
n=0 from cursor to end of display,
n=1 from begin of display to cursor,
n=2 entire display.
EL E[nK Erase part or all of line: ce
n=0 from cursor to end of line,
n=1 from begin of line to cursor,
n=2 entire line.
ECH E[nX Erase n characters --
SU E[nS Scroll display n lines up (forward) sf
SD E[nT Scroll display n lines down (reverse) sr
SGR E[nm Set character attributes: --
n= 0 normal attribute (all off)
n= 1 bold (highlight)
n= 4 underscore (if supported by HW)
n= 5 blink (if supported by HW)
n= 7 reverse
n=3X set foreground color (see table)
n=4X set background color (see table)
X=0 black X=1 red
X=2 green X=3 brown
X=4 blue X=5 magenta
X=6 cyan X=7 white
-- E[=p;dB Set bell pitch (p) and duration (d), --
picth is in units of 840 nS,
duration is units of 0,1 S.
-- E[=s:eC Set cursor start and end scanline, --
start on line s, end on line e.
-- E[=nA Set the border color to color n
(see table) (if supported by HW)
-- E[=cF set normal foreground color to n --
(see table)
-- E[=cG set normal background color to n --
(see table)
-- E[=cH set reverse foreground color to n --
(see table)
-- E[=cI set reverse background color to n --
(see table)
n= 0 black n= 8 grey
n= 1 blue n= 9 light blue
n= 2 green n=10 light green
n= 3 cyan n=11 light cyan
n= 4 red n=12 light red
n= 5 magenta n=13 light magenta
n= 6 brown n=14 yellow
n= 7 white n=15 light white
note: the first E in the sequences stands for ESC (0x1b)
.Ed
.Pp
.Sh AUTHOR
Søren Schmidt
Email: (sos@login.dkuug.dk -or- sos@kmd-ac.dk)
