ZX Computings - OpenLibra

It can be pretty hard trying to
decide which computer you'll
buy. For the benefit of those
unlucky souls who do not yet
own a ZX81, Peter Freebrey
takes a close look at the
ZX81, and compares it with
its predecessor, the ZX80.
The ZX81 gives the
impression of being more
robust than the ZX80, and
although the keyboard is still
the now familiar 'touch type'
as on the ZX80, I find the
slightly textured matt finish
gives me a greater feeling of
control than its glossy
forerunner. The ZX81 comes
complete with separate mains
power supply and leads to
connect it to your TV set and
tape recorder. The 21 2-page
instruction manual is
How good is the ZX81? How does
it compare with the ZX80? Does
it represent a good buy for
£69.95? we attempt to answer
these questions for you.
comprehensive and is
Sinclair's best yet. The ZX81
uses the new 8K ROM which
was announced in 1980.
There are some 20
commands and/or statements
that were not available to the
ZX80. From the list of these in
Table 1 you can see that they
include the option of a FAST
or SLOW mode — this is
Review
certainly a useful
improvement. When running in
the FAST mode the ZX81
operates in a similar manner to
the ZX80 '— fast operation,
with a very noticeable flicker
on the display whenever a key
is operated or command
actioned together with a blank
grey screen while
computations are taking place.
In SLOW mode operation you
get a flicker-free picture.
Although the ZX81 does
not have a memory mapped
display, it refreshes and
updates the screen
information while still
proceeding with the program it
is running. This mode is much
slower in operation: a FOR .. .
NEXT loop of 10000 takes
1 76 S in SLOW and 44 S in
FAST mode. Even though
SLOW realty does mean
slower operation it gives the
user the option of using
moving graphics-apart from
making the display less of a
strain to the eyes I
Whereas the ZX80 was
limited to integer calculations
the ZX81 has a full floating
point notation and this has
ZX COMPUTING SUMMER 1982