Read Console Buffer
===================

CP/M call 10, Read Console Buffer, has a range of additional facilities.

The read buffer reads a line of edited console input into a buffer
addressed by registers DE. Console input is terminated when either the
buffer overflows, or on control J or control M.

The Read buffer is of the form:

::

    DE | +0 | +1 | +2 | +3 | +4 | +5 | ...... | +N |
       | mx | nc | c1 | c2 | c3 | c4 | ...... | ?? |

where *mx* is the mamimum number of characters the buffer will hold (1
to 255).

*nc* number of characters read (set by DEMOS on return). *nc* is
followed by *c1*, *c2*, etc., the characters read from the console.

If *nc* < *mx* then uninitialised positions follow the last character
(represented by ?).

A number of control functions are recognised during line edit:

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Control Key Action
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Control C   reboots system if at start of line
Control E   causes physical end of line
Control H   backspace one character position
Control J   terminate input
Control M   terminate input
Control R   retype current line after new line
Control X   backspaces to beginning of current line
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