After reading INMC80 Issue 3 I realised I was in a position to help many
The Space Invaders game published in Issue 2 is the same one that a friend of
mine bought. The program needs a little explanation:
1. The graphics option that is incorporated is for use with the William Stuart
Graphics System although gives a reasonable display with NAS-GRA.
2. The program will work with any Nascom monitor – T2, T4, B-Bug, NAS-SYS 1.
(NAS-SYS 3?) (Yes – Ed.)
3. There is a ‘Pause’ command, operated by hitting the ‘P’ Key. This temporarily
stops the program so you can answer the telephone etc. Hit any key to resume play.
The answers to W. Squires’ letter are:–
1. The program was written to run at 2MHz not the normal NASCOM 2 speed of 4MHz.
2. There are 3 places where the program has to be changed for different keys. The
first two places display and check for those keys not available as the fire key. The
bytes at 1058H and 105CH must be changed to check for the ACSII values of these keys.
Lastly the codes at 1785H must be altered. This piece of code scans the keyboard, then
looks for various keys in the keyboard map at 0C01H. Using the routine at the end of
this letter it is possible to work out which bits of which bytes are altered by the
keys you have chosen.
e.g. To substitute the ‘A’ and ‘X’ keys for ‘↓’ (CD) and ‘→’ (CR)
1040 0B/1042 N/L (HEX VALUE FOR A ‘↓“)
1042 09/1058 N/L ( " " " " ‘→“)
1058 14/105C N/L ( " " " CURSOR DOWN)
105C 12/1785 N/L ( " " " " RIGHT)
1785 3A 04 0C/178B N/L (CURSOR DOWN KEY ALTERS 0C04H
178B FE 40/1790 N/L (bit 6.)
1790 3A 05 0C N/L (CURSOR RIGHT KEY ALTERS 0C05 H
1793 FE 40. (bit 6.)
As regards David Parkinsons letter, I feel that the documentation on the
Nascom 2 is very good indeed, particularly the invaluable listing of NAS-SYS. The
documentation on his toolkit is more than adequate and I had no problems learning to
The article entitled “WHERE” must have been written by a beginner to produce
such a piece of code. Try the following:–
RCAL LOCN D7 00 (MONITOR RTN).
LOCN: POP HL El
The address of “LOCN” is popped into HL.
Please warn NASCOM owners about writing BASIC programs with variable names
longer than 2 letters. Although it is acceptable to do so, MICROSOFT BASIC V4.7 only
stores the first 2 characters of the variable names and therefore cannot distinguish
between 2 different variables having the same first 2 characters. This also applies to
Finally could you print your prices for advertising in INMC80, as a friend and
I have started a software firm to seel NASCOM Software for the NASCOM 2, and we would
like to advertise in INMC80.
A. READ, Chelmsford, Essex.
(Rates are 100.00 per full page, part pages are charged proportionately – Ed.)