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What is the difference between the hp 39g, hp 40g & hp 39g+?
At the time that the hp 39g was designed, as an upgrade from the original
hp 38g, there were two competing sets of requirements. The European
market wanted a calculator which had a CAS system but they were highly
distrustful of the infra-red communication which was standard on the hp 38g,
feeling that it might allow cheating in examinations. The US and Australian
markets, on the other hand, wanted the infra-red communications but their
educational systems were not yet prepared to allow the power of a CAS into
their classrooms, feeling that it did too much of the students’ work.
The solution adopted was to use the same chip for two calculators, the
hp 40g and the hp 39g. These two models have, respectively, infra-red but
no CAS and CAS but no infra-red. They are otherwise identical except for the
label below the screen. The calculator’s chip is able to detect which model it
is in and activate or de-activate the CAS accordingly.
The hp 39g+, released in 2004, is an upgraded model of the hp 39g, the
differences being vastly greater speed and the extra Finance aplet.
If you own an hp 39g and you are wondering if you can fool it into believing
that it is an hp 40g and thereby activate the CAS, then please don’t try it. If
you disable the infra-red by, for example, cutting the internal wires then you
won’t have an hp 40g - you will simply have a crippled hp 39g. Nor is it
possible to activate the CAS by means of a special program. It is possible to
partially activate it but the result will be crippled to varying degrees and will
not work properly, possibly even giving incorrect answers. In addition to this,
any education system will very probably regard this as a serious instance of
cheating if you use it in an examination and penalize you accordingly.
If you own an hp 39g+ then the question does not even arise because the
code for the CAS was left out of the chip when it was upgraded to become
the hp 39g+.