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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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