Using The Keyboard Under Cp/M - Epson PX-8 User Manual

3.4 Using The Keyboard Under CP/M
Since CP
1M
has been designed as a universal operating system, it does not neces-
sarily allow all the special keys on the PX-8 to function as they do in BASIC
or in some applications programs. In particular the cursor keys are not sup-
ported by
CP/M.
Some of the special keys behave differently. The following
summarises the use of the different functions available form the keyboard when
the PX-8 is on the CP
1M
command line. They do not hold for the MENU com-
mand line.
3.4.1 Using the programmable function keys
The keys
~
to
I
PF5
I
and their shifted counterparts can be used to print the
common CP
1M
command words, thus preventing errors and saving time. When
setting them up, it is worth ensuring that trailing spaces are included to con-
form with the requirements of CP
1M.
The key display is normally absent from
the lowest line of the screen but can be switched on using the CONFIG pro-
gram. Another alternative in deciding which key provides which string is to use
the attached Programmable Function key label. The CONFIG program also
allows alteration of the strings given by each key.
3.4.2 Line termination commands
When you have entered a command, you must tell CP
1M
that you have finished.
There are three key commands to do this:
The
I
RETURN
I
key is the simplest way to enter a command.
A
I
CTRL
I -
[MJ
is equivalent to a pressing the
I
RETURN
I
key.
A
I
CTRL
I -
QJ is equivalent to a line feed. On the CP
1M
command line it
also causes the command to be entered as though you had pressed the
I
RETURN
I
key.
3.4.3 Character deletion commands
If a mistake is made, it is necessary to correct it. This can be done in two ways,
but the CURSOR KEYS CANNOT BE USED.
I
CTRL
I -
[Hl or the BS (backspace) characters delete the character to the left
of the cursor from the screen and move the cursor one step back.
The [QKJkey causes the key to the left of the cursor to be deleted, but also
repeats the deleted character on the screen. lethe
~
or
I
CTRL
I -
[Hl is used
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to delete another character it will place the cursor one place to the left of this
deleted character because any characters deleted by the[QKJkey do not exist
except on the screen.
3.4.4 Line deletion commands
Sometimes it is necessary to delete a whole line when a mistake is made or for
other reasons. There are two ways to do this:
00
will backspace to the beginning of the line, erasing all of the text.
I
CTRL
I -
[Q]
will place a "
# "
character at the end of the line and then place
the cursor on the next line ready to start over again. This is useful, because
the incorrect command is still present on the screen, although it has been erased.
3.4.5 Display control commands
There are a number of control key sequences which can be used to handle the
screen display. Again not all the special keys work, although some can be made
to perform their function to a limited extent.
The
I
CLR
I
key can be used to clear the screen, although it is not supported by
CP/M. It
is equivalent to a
I
CTRL
I - UJ .
Typing either of these commands
causes the CP
1M
command line to show:
Pressing the
I
RETURN
I
key will clear the screen, printing a question mark in the
top left hand corner. The system prompt will be placed on the third line. This
is because if you give CP
1M
a command it does not understand it will repeat
the command followed by a question mark and return the system prompt.
I
CTRL \ -
[f]
can be used to overflow on to the next line before the user has
pressed the
I
RETURN \
key. This is useful if the screen is split (screen mode 1
or 2), as it enables a new word to be written on to a new line so that it can
be read more easily. The" #" character is placed at the end of a
l~ne
when
using the \ CTRL \ -
[Q]
or
I
CTRL \ -
[BJ command to show it is a terminated
line, to distinguish it from a
1
CTRL \ -
[f] .
I
CTRL \ -
[BJ is used to repeat a line with the errors removed if you are a bad
typist and using the
I
DEL
I
key frequently. For example if you type an "R" in-
stead of a "T" in the "STAT" command, and ha(Cdeleted the
"R"
using DEL,
and pressed
I
CTRL \-
[BJ
keys after typing "T" again the screen would show:
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