NAS-SYS 3 – IMPROVED VERSION OF NAS-SYS 1
1. All the keys on the keyboard automatically repeat when held
down, (Not the @ key.) The initial repeat delay and the repeat
speed are adjustable.
2. All routines are interruptable, so that interrupt can be used
while executing NAS-SYS routines.
3. The CRT routine allows data to be output anywhere in memory,
so headings can be output to the top line of the display.
4. The Read command has an optional parameter which allows cassette
tapes to be read into any memory locations.
5. The Tabulate command is enhanced in three ways. Firstly, ASCII
values of the bytes are output as well as the usual hexadecimal
tabulation. Secondly, a fourth parameter can be used to specify the
output of additional values on each line, to allow for printers of
different widths. Thirdly, a fifth parameter allows suppression of
either the hexadecimal output or the ASCII output.
6. All NAS -SYS routines can be single stepped, which makes it
easier to test a program which uses NAS-SYS routines. By using the
repeat keyboard feature, high speed single stepping is possible.
7. The register display is enhanced so that it shows the two byte
value pointed to by each of the main registers.
8. Output from the Modify command is displaced two characters to the
right, to improve readability.
9. The External (X) command has additional options, and no longer
fails to output nulls. This enables the NULL command in BASIC to
10. There are three new commands. P displays the stored user
program registers. D executes a program at D000H and Y executes a
program at B000H.
11. The cursor blink rate is adjustable.
12. There are three new routines. Repeat keyboard scan, Output
two spaces, and a new routine which can execute any other routine.
13. Both on breakpoint and on NMI, control passes through the $NMI
jump before displaying the registers, allowing a program to take
14. The B 0 command turns off the breakpoint completely, so that
with appropriate hardware NAS-SYS can be executed in RAM.
15. Support in NAS-SYS itself for the use of paper tape has been
removed, so there is no longer a Load command and the Tabulate
command does not output a checksum.