80-Bus News

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 warm boot.

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 correctly.