INMC 80 News

  

June/July/August 1980, Issue 1











Page 40 of 48











Assemblers

ASSEMBLERS & NAS-SYS

By R. O’Farrell

Pending the availability of Zeap 2.0 at a reasonable price to existing users of Zeap 1.0 who have changed to Nas-Sys, a patch tape from DJ Sotware renders your existing ZEAP fully usable on Nas-Sys. DJ Software are the suppliers of Revas tapes (blessed by many who couldn’t wait for PCW to finish publishing the program), and this patch tape (price 7.50) will probably prove more useful. The conversion is child’s play for T4/B-Buggers (sounds very doubtful, that), but a little bit trickier for T2 users. Under your old monitor, you write a copy of the Zeap to tape using the ‘W’ command on T4/B-Bug, or ‘D’ on T2. Then you power down and change from the old monitor to Nas-Sys. Load the Zeap tape you have just written (’R’ command on T4/B-Bug) Here is where T2 users have difficulty. They will have to write a small input routine to scan the input for Nascom backspace, clear screen and new line, and substitute ASCII characters for them. In any event, when the Zeap is loaded, do NOT attempt to execute it. Instead, play the patch tape into the machine. (No need for any commands). The patch tape will perform a series of modifications and insertions, which consist for the most part of replacing all system calls with the Nas-Sys ‘RST’ and ‘SCAL’ number, and a padder NOP to fill the three byte space. There are also a number of calls to an approx 300 (dec) byte extension at 1B08H. All this is done automatically by the tape. When the tape has finished, you can now enter Zeap (E F00) in the usual way. The tape is fully commented, in the sense that it tells you at all times what it is doing (but not necessarily in very great detail) and it is accompanied by a five page commentary sheet, which is hard copy of the tape.

On entry, you will notice one difference: the top line message is now on the second line from the top, and the serial number of your copy is replaced by “OPTION 00”, with whatever option is set displayed. This top line performs a very useful function it blanks out when the Assembler cannot accept a command, and restores when it can. The V (list) command now lists in blocks of eight lines (Newline to continue, any other key to terminate) and the F (find) command allows you to tell it what line to start or continue the search at. The N (Nas-Sys) exit command, when used with two arguments, allows lines of entry to be written to tape or externally with no line numbers – a simple text handler.

A very useful patch, allowing one to dispence with the schizophrenia of using and thinking for two monitors.

Zeap 2.0 would be useful as it gives a symbol table, (and possibly paginated listing ? (no – Ed.)), but having spent 30.00 on Zeap 1 I doubt if many will be tempted to spend the same amount on Zeap 2.

Those who are tempted to disassemble their Zeap 1 with Revas, or a similar disassembler, will find that F00H to F70H (approx) consist of workspace and data areas, and 1003H to 1268H consists of the dictionary These should be defined as data areas for the disassembler. There may also be minor unpleasantness wherever a Restart is used under Nas-Sys, but they can be coped with.


This is an OCR’d version of the scanned page and likely contains recognition errors.











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