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Casio PB-
700
hand-held computer
Personal computers seem to be developing
along four separate lines: desk, portable, lap-
type and hand-held. Here we review Casio's
latest hand-held computer, the PB- 700.
Compared with lap-type computers
such as the Tandy Model 100 or Canon
X-07, the Casio PB-700 is really small, at
less than half the size. It measures 200 x
88 x 23mm (W x D x H) and weighs a
mere 315 grams, including the batteries.
The keyboard is split into two sections
with alphabetic on the left (QWERTY-
style) and numeric keypad on the right.
In all, there are 58 keys, most of which
provide a particular control function.
Basic is used as the programming
language and to make things easier, the
most-used commands are entered by only
two key presses.
Memory
Up to 10 programs can be stored and
any program can be accessed by two key
presses. Memory capacity of the PB-700
is 4K of RAM which can be extended to
a maximum of 16K by the addition of
three 4K RAM modules. Note that the
amount available for the user is 1232
bytes less than the amount of RAM
installed because the first 1232 bytes is
required by the PB-700 itself.
The liquid crystal display format is
four lines of 20 characters each. This is a
lot less than the Tandy Model 100 for
example (8 lines x 40 characters) but for
a lot of applications it is quite adequate.
As with most liquid crystal displays,
the viewing angle is relatively small,
particularly the vertical viewing angle.
This problem is overcome to an extent by
the contrast control. This really should
be called the "viewing angle" control
since it alters the polarising voltage on
the display.
However, even when viewed at the
optimum angle, the contrast of the
PB-700 display is not particularly good.
This should not be a real drawback
though, unless the unit is to be used for
long periods at a time.
On the other hand, while some
calculators using liquid crystal displays
seem to have an overly long keyboard
response time, the PB-700 is very fast.
While it is not possible to touch-type on
the closely spaced keys, even very fast
key presses do not catch the unit out.
The character format is 8 x 5 dots and
lower case characters such as y have true
descenders when they are actually
displayed. Normally though, all
characters are displayed in upper case,
even though they are held in memory in
upper and lower case for subsequent
printout if required.
Power supply for the PB-700 is from
two battery sources. The main supply is
four 1.5V penlite cells while a lithium
battery powers the RAM for program
retention.
Casio recommend replacement of all
five batteries after two years to avoid
possible damage due to leakage of
battery contents. However, in normal
use the main batteries may have to be
replaced more often than that. Estimated
life of the penlite cells with continuous
use is about 100 hours. Compared with
the usual battery life of the larger lap
computers, this is very good.
To conserve the batteries, the PB-700
has an automatic power-down feature to
switch the unit off eight minutes after
the last keyboard entry, unless a program
is running.
1 1 6
ELECTRONICS Australia, November, 1984
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