Basic Disk Operating System (BDOS) Functions
The Read Console Buffer function reads a line
of
edited console input from the
logical console device (CONSOLE) into a buffer addressed by register DX. Console
input
terminates when the
input
buffer
is
filled,
or
when either a
return
(CONTROL-M)
or
line feed (CONTROL-J) character
is
entered.
The
input buffer
addressed by
DX
takes the following form.
DX:
+0+1
+2+3+4+5+6+7+8
...
+n
Imxlncl ell
c21
c31
c41c51c61
c71·
.
·1
??
I
where
mx
is
the maximum number
of
characters which the buffer will hold,
and
nc
is
the
number
of
characters placed in the buffer. The characters entered by the
operator
follow the nc value. The value
mx
must be set
prior
to making a function
10
call
and
may range from 1
to
255. Setting
mx
to
zero
is
equivalent
to
setting
mx
to
one. The value nc
is
returned
to
the calling
program
and
may range
from
0
to
mx.
If
nc
is
less
than
mx, then uninitialized positions follow the last character, denoted by
"??" in the diagram. A terminating return
or
line feed character
is
not
placed in the
buffer
and
not included in the count
nco
The line editing control functions supported during console input
under
function 1 0
are summarized in Table 4-3.
Table 4-3 Line Editing Controls
KEYSTROKE
RESULT
DEL
Removes
and
echoes the last character
CONTROL-C
Reboots when
at
the beginning
of
line
CONTROL-E
Causes physical end
of
line
CONTROL-H
Backspaces one character position
CONTROL-J
Terminates input line (line feed)
CONTROL-M
Terminates input line (return)
CONTROL-R
Retypes the current line after new line
CONTROL-U
Removes current line after new line
CONTROL-X
Backspaces to beginning
of
current line
Certain functions which return the carriage
to
the leftmost
~OSlt10n
(e.g.,
CONTROL-X) do so only
to
the column position where the
prompt
ended. This
convention makes
operator
data
input
and
line correction more legible.
4-9
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