|one of the many 531 variations. this one slightly more
recent and not so well made as the earlier kind. supplied with the modern
hard front cover that slides off to fit behind the machine when in use.
the screen is unimpressive, rather small and difficult to read,
although the 10+2 digits is most welcome. the buttons are a bit more
plastic than usual, but nevertheless adequate. the delete key is useful.
functionally, it has the usual features of a scientific calculator,
fractions are a bonus but stats are only in one dimension missing out on
linear regression and correlations. combinations and permutations (nCr
& nPr) are slightly lame, not being able to calculate 70C6, for
example (70! fails internally).
it powers by two AA cells that fit inside the machine. you have to undo
the four screws and dismantle the machine to replace them. i presume that
once fitted they last for decades, like the casio fx-180p.