<P> Solar - powered calculators are hand - held electronic calculators powered by solar cells mounted on the device . They were introduced at the end of the 1970s . </P>
<P> Solar - powered calculators are hand - held electronic calculators powered by solar cells mounted on the device . They were introduced at the end of the 1970s . </P>
when was the first solar powered calculator invented
when was the first solar powered calculator invented
end of the 1970s
end of the 1970s