Printing When On The Cp/M Command Line; The Concept Of Logical And Physical Devices - Epson PX-8 User Manual

A> STARRT #
STAT
The ~ key performs the same function as
I
CTRL
I -
[BJ .
The
I
PAUSE
I
or
I
CTRL
1-
~
key can be used to temporarily halt the screen scroll-
ing. For example if a DIRectory has too many files to fit in the screen window,
pressing either the
I
PAUSE lor
I
CTRL
I -
~
keys will stop the display until another
key is pressed, enabling the text to be read. The shifted cursor keys can also
help with this problem as described below.
The SHIFTED CURSOR KEYS (
[!] and [IJ ) can be used to scroll the
real screen window up and down the virtual screen. Thus if a long DIRectory
has scrolled off the real screen, these keys can be used to bring it on again.
The
I
CTRL
I
and CURSOR KEYS (
G
and @ ) can be used to change
the displayed virtual screen in modes 0 and 1 and the cursor position in screen
mode 2. For example a DIRectory can be stored on one virtual screen while
a program is used on another. Care must be taken in using this facility. Full
details are given in section 2.2.6.
The! SCRN !key can be used to lock the real screen window on part of the virtual
screen. This is described in section 2.2.6.
3.5 Printing When On The CP 1M Command Line
There are two ways to print when on the CP
1M
command line.
The !
CTRL
I
and !
PF5
! key can be used to dump the contents of the screen to
the printer.
I
CTRL
I -
~
can be used to toggle the echoing of text to the printer. The first
time !
CTRL
I -
~
is pressed anything output to the screen is simultaneously
sent to the printer. Pressing ! CTR!,] -
~
a second time only sends input to
the screen. This can be used in utility programs, but may not work in applica-
tions programs.
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e ,
,...
~
...""
C;,
.~
~) .~
C;, . .
~
,
3.6 The Concept of Logical And Physical Devices
As a universal operating system, CP
1M
has to have a means of communicating
with all the devices associated with a computer in a general way. The software
in each computer is then connected to the devices which are unique to that par-
ticular computer. This is achieved through the use of the concept of logical (sym-
bolic) device names in CP
1M
being assigned to physical (actual) devices
supported by the computer. Such a concept considerably simplifies the use of
the computer.
NOTE:
In practice assignments are carried out by the use of the CONFIG program
described in section 3.8. This allows various devices to be assigned using com-
mon names, rather than following the normal CPIM system. The description
outlined below
is
presen tedfor completeness, andfor thosefamiliar with CPIM,
who wish to use the STAT program (section 3.8) to change assignments.
3.6.1 The logical devices
There are four logical devices in CP
1M
which correspond to the types of devices
which one would expect with a computer. They are given the symbols CON:,
RDR:, PUN:, and LST: from the names associated with their functions.
CON: denotes the CONsole device, which is the means of allowing data to
be input by and output to the user. In the case of the PX-8 it would correspond
to the keyboard and LCD screen.
RDR: denotes the ReaDeR device, which receives information from another
source. The name originally derives from a paper tape reader, but in the PX-8
is normally the RS-232C device.
PUN: denotes a device to output information. Its name derives from a paper
tape PUNch. In the PX-8 it is normally assigned to the RS-232C port.
I,s1': denotes the output LiST device, normally a printer.
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