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.Chapter Video editing
.HL1 Introduction
.index ^Video mode
 TECO has the facility for displaying a portion of the
text being edited on the screen of a video terminal and updating
the display as commands are being executed.
This mode makes it unnecessary to explicitly have
TECO type out text to verify where one is in the text,
or what changes have been made.
All commands are typed the same way in video mode as they are
while not in video mode, the only difference is the display.
 In video display mode, TECO will normally display text around
the pointer, which will be represented on the screen
by the cursor.  Therefore the character the cursor is positioned under is the
character position just after the pointer.
If the pointer is moved outside the bounds of the displayed text,
a different portion of the file will be displayed.
Several "immediate" commands are available for moving the pointer
with a minimal amount of typing.
 To enter video mode, TECO must be told on which lines of
the screen to display the text, and where to display the commands from the
terminal.  Special commands and Q-registers are provided for this purpose.
.HL1 Video mode editing
.index ^Video mode
The video mode editing is entered by a combination of the E_$ and EV commands.
.index ^Command ><E_$
.index ^Command ><EV
The E_$ command is used to define a what Q-register to display on what
lines on the screen, while the EV command is used to turn on/off the video
processing to and define the type of terminal that is being used.
.hl2 E_$ Command
.index ^Command ><E_$
The E_$ command defines the lines that a Q-register will be displayed on.
The format of the command is:
.b.i+5
&*n,mE_$(Q-reg)_$
.b
The n and m arguments are numeric arguments that specify the line numbers
that the Q-register is to be displayed on.  The Q-register is the item
that is enclosed in the parens after the E_$ command.  An example of
the E_$ command would be:
.b.i+5
&*1,19E_$(TEXT-BUFFER)_$20,24E_$(COMMAND-BUFFER)$$
.B
This command would cause the text buffer to be displayed on the first
through the nineteenth line.  The command buffer would then be displayed
on the 20th through 24th lines.
.hl2 EV
.index ^Command ><EV
The EV command is used to specify either a video parameter or a terminal
type.  The terminal types that are currently supported in TECO
are:
.lm+20.ts20
.B.I-20
^&Type\&	^&Comment\&
.b.i-20
.index ^Terminal type ><TTY
TTY	Hardcopy terminal.
.b.i-20
.index ^Terminal type ><CRT
CRT	CRT terminal that is currently not supported.  Deletes will cause
the cursor to be backed up a space output to clear the 'deleted' character.
.b.i-20
.index ^Terminal type ><ACT4
ACT4	ACT4 terminal.  No full video support.
.b.i-20
.index ^Terminal type ><ACT5
ACT5	ACT5 terminal.  No full video support.
.b.i-20
.index ^Terminal type ><ADD580
ADD580	ADDS 580 terminal.  No full video support.
.b.i-20
.index ^Terminal type ><ADM2
ADM2	Lear Sigler ADM-2 terminal.  No full video support.
.b.i-20
.index ^Terminal type ><ADM3
ADM3	Lear Sigler ADM-3 terminal.  No full video support.
.b.i-20
.index ^Terminal type ><ADM3A
ADM3A	Lear Sigler ADM-3A terminal.  Full video support.
.b.i-20
.index ^Terminal type ><BEE
BEE	Beehive terminals.
.b.i-20
.index ^Terminal type ><CDC
CDC	CDC terminal (?).
.b.i-20
.index ^Terminal type ><DM1520
DM1520	Datamedia 1520 and 1520A terminals.  Full video support.
.b.i-20
.index ^Terminal type ><DPT
DPT	Datapoint terminal.  No full video support.
.b.i-20
.index ^Terminal type ><H19
H19	Heathkit H19 terminal.  Full video support.
.b.i-20
.index ^Terminal type ><H19A
H19A	Heathkit H19 terminal in ANSI mode.  Full video support.
.b.i-20
.index ^Terminal type ><H1200
H1200	Hazeltine 1200.
.b.i-20
.index ^Terminal type ><H1500
H1500	Hazeltine 1500.
.b.i-20
.index ^Terminal type ><H1420
H1420	Hazeltine 1420.
.b.i-20
.index ^Terminal type ><H2000
H2000	Hazeltine 2000.
.b.i-20
.index ^Terminal type ><HMOD1
HMOD1	Hazeltine Modular I.
.b.i-20
.index ^Terminal type ><HMOD1I
HMOD1I	Hazeltine Modular I with insert/delete line.
.b.i-20
.index ^Terminal type ><HP2621
HP2621	HP 2621.
.b.i-20
.index ^Terminal type ><HP2640
HP2640	HP 2640.
.b.i-20
.index ^Terminal type ><HP2648
HP2648	HP 2648.
.b.i-20
.index ^Terminal type ><RGNT25
RGNT25	ADDS Regent 25.
.b.i-20
.index ^Terminal type ><TELRAY
TELRAY	Teleray terminals
.b.i-20
.index ^Terminal type ><TELVID
TELVID	Televideo terminals
.b.i-20
.index ^Terminal type ><TK4025
TK4025	Tektronics 4025 terminal.
.b.i-20
.index ^Terminal type ><VT05
VT05	Digital Equipment Corporation VT05 terminal.
.b.i-20
.index ^Terminal type ><VT100
VT100	Digital Equipment Corporation VT100 terminal.
.b.i-20
.index ^Terminal type ><VT132
VT132	Digital Equipment Corporation VT132 terminal.
.b.i-20
.index ^Terminal type ><VT50
VT50	Digital Equipment Corporation VT50 terminal.
.b.i-20
.index ^Terminal type ><VT52
VT52	Digital Equipment Corporation VT52 terminal.
.b.i-20
.index ^Terminal type ><VT61
VT61	Digital Equipment Corporation VT61 terminal.
.b.lm-20
.ts 8,16,24,32,40,48,56,64,72,80
 The video parameters that can be read or set with the EV command are:
.lm+20.ts20
.B.I-20
^&Parameter\&	^&Comment\&
.b.i-20
.index ^Video parameter ><LINE
LINE	
.B.I-20
.index ^Video parameter ><MODE
MODE	
.B.I-20
.index ^Video parameter ><NODE
NODE	
.B.I-20
.index ^Video parameter ><OFF
OFF	This keyword will turn the video mode editing off.  It is the inverse
of the ON keyword.
.B.I-20
.index ^Video parameter ><ON
ON	This keyword will cause the video mode editing to be turned on.
The E_$ and EV_<Terminal-type_>_$ will have no effect until the video
editing is 'turned on' with this keyword.
.B.I-20
.index ^Video parameter ><REFRESH
REFRESH	
.B.I-20
.index ^Video parameter ><SCREEN
SCREEN	
.B.I-20
.index ^Video parameter ><SCROLL
SCROLL	
.B.I-20
.index ^Video parameter ><TRMOP
TRMOP	
.B.I-20
.index ^Video parameter ><UPDATE
UPDATE	
.B.I-20
.index ^Video parameter ><WINDOW
WINDOW	
.LM-20
.TS 8,16,24,32,40,48,56,64,72,80