effectively in screen edit mode all the time. This was very useful when, for
example, editing BASIC programs, as you did not have to remember to enter screen
edit mode before editing each line. Now this feature is available with SYS and
CP/M, using the new ‘fixed’ screen edit mode.
To enter ‘fixed’ screen edit mode, enter screen edit mode, and then again
press the key which activates full screen editing. This makes the cursor on the
IVC change to a solid non-blinking block, and this means that you are permanently
in screen edit mode. As before, press the Return or Enter key to enter a line as
input. When CP/M requests the next input character, screen edit mode will
automatically be reactivated. To escape from this mode, press the key a third
time. This feature is particularly useful when editing BASIC programs, as a LIST
command can be followed by extensive editing of the lines displayed, without
having to remember to enter screen editing mode for each line.
Screen Paging Control
Another improved feature of SYS is control over screen paging. If too many
lines are output to the screen without any input being obtained from the
keyboard, then it is possible that information might roll off the top of the
display and be lost. Whenever this could occur, the following message is output:–
"*** Press ^C, ^S, R, W, K or Space ***"
If you press Control/C or Control/S then this character is returned as the
next input character to the program being run.
If you press R then the screen paging feature is disabled until the next
user input. For example it would start to operate again if Control/S was used to
pause the output display.
If you press W then the screen paging feature is disabled until the next
If you press K then the screen paging feature is disabled until the next
cold boot, or until SYS is executed.
If you press a space then the next page of output is displayed.
MAP 256K RAM
SYS now provides full support for the MAP 256K RAM card, allowing virtual
disk systems with up to a total of one megabyte of RAM. This is described in more
detail elsewhere in this issue. SYS uses the new 32K paging method for the Nascom
and Gemini GM811, and with the GM813 it uses the full memory mapping capabilities
of the GM813 and of the MAP RAM. SYS provides warm boot off the virtual disk, and
this speeds up this process considerably. It also has the advantage that you
don’t need to worry about having the correct data on the system tracks of your
disks, as these are no longer used except on cold boot.
Restructuring of SYS
In order to allow the support of three different types of virtual disk, as
well as the inclusion of two completely separate versions of the disk software,
SYS has had to be restructured. It is now much more easily maintainable, as the
different parts are stored in eight separate source modules. These are SYSB1.MAC
to SYSB7.MAC, and SYSB6A.MAC which contains the alternative standard disk
software. As usual the user has only to edit SYSB1.MAC, which now contains only
the option switches and various helpful comments, and then submit SYSB.SUB, which
does the assembly and link. This takes about five minutes, which is very fast
considering the size of code which is being processed. M80 actually stops and
thinks to itself for a bit when it has to generate all the relocation labels, so
there is no need to worry if your system becomes silent. The M80 assembler and
L80 linker are required, and I recommend release 3.44, which I know to work