NAS-SYS 3

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 work correctly.

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 alternative action.

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.