ZX Computings - OpenLibra

* REQUIRE 16K RAM
HEWSON
CONSULTANTS
HINTS AND TIPS for the 2X81 by Andrew Hewson
£4.25
"Good value and quite fascinating a very inexpensive way ol
acquiring months of programming experience" YOUR
COMPUTER Nov 81.
"Excellent very good value for money" SYNC
Saving Space Understanding the Display File Converting
ZX80 Programs Chaining Programs (pass data between
programs, call subroutines from cassette, establish data files*
Machine Code Programs (write, load, edit, save and debug
machine code)
Routines and programs are scattered liberally throughout the text
and the final chapter consists of twelve useful, interesting and
entertaining programs
16K RAM PACK £37.50
A top quality add-on 16K dynamic memory specially designed tor
the ZX81 Simply plugs into the port at the back of your Sinclair
Can be used in conjunction with the ZX printer Neatly packaged
in a black plastic she' 1 to match your ZX81 incredible value, why
pay more?
SPECIAL OFFER a free copy of our super Space Intruders
cassette will be sent with every 16K RAM order before 1 5 82
Z80 OP CODES £1.45
A must for the beginner and the experienced programmer alike
This handy ready reckoner lists all 600 plus Z80 machine code
instructions in decimal and hexadecimal with their mnemonics.
Each Op code is succinctly explained and cross-referenced
Supplied m a protective transparent wallet for easy reference and
durability.
MEMOPACK 64K RAM £79.00
Developed by Memotech this amazing 64K RAM needs no extra
power supply Simply plugs neatly and lirmly into the rear port of
your 2X81 Can be used with the ZX printer and other add on
hardware
(Mail Order DeptE )
99 East St, Epsom Surrey, Tel 03727 21215
quoting your credit card 24 hr phone service
Air IVIail Europe plus 70 p Elsewhere plus 111.7i)J
Just look at these features
* 8 16K can be switched in and out in 4K blocks to leave space
for memory mapping.
* 12-16K can be proiected against overwriting during loading
from cassette.
' Directly addressable and user transparent
* Up to 15K of basic program area
" 32K or more of variable area
PROGRAMMERS TOOLKIT £6.50
Are you writing your own programs for the ZX81? Then use our
TOOLKIT to do the donkey work Copy into RAM before you
start work and then you will have it at your fingertips
Comprehensive LINE RENUMBER including GOTOs and
GOSUBs; LOAD. EDIT and RUN machine code programs.
INSPECT the ZX81 system routines; COPY them mio RAM and
PATCH and/or EXTEND them, FIND a given piece of Basic code
and REPLACE all occurrences of it, move blocks of Basic lines
with EDIT.
SPACE INTRUDERS £5.95
40 alien ships in each squadron. All acnon
display Automatic option the machine
plays itself - can you do better? Written in
machine code for super fast lun. Squadron ^
after squadron attack your position Three .
laser bases. Full score display.
STATISTICS
Three programs on the one cassette
1) il Statistics — prints the curreni mean and standard deviation
after each value ts entered
ill Regression prints the current mean and standard deviation
of the y and x values and the intercept and slope of the
iegression line.
nil Trend - prints the current mean and standard deviation of
the y and x values and the intercept and slope of the trend
lines.
2) CHI SQUARED TEST - prints the current value of the Chi
squared statistic and the current sample size
3) GRAPH PLOT plots a graph cf data entered from the
keyboard.
Cheque with order or quote Access or Barclaycard number
to: HEWSON CONSULTANTS Dept L. 7 Grahams Close.
Blewbury, Didcot. Oxon OX11 9QE. TEL: (0235) 850075
100 ZX COMPUTING SUMMER 1982
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£3.75