HP calculators
Hewlett-Packard was famous for its range of pocket calculators. These are some of its calculator models.
HP-20S
A very good quality algebraic programmable. Commands a higher than normal price for this type of calculator since it is programmable and very well made. Measures or compares well with the older Ti-55, 60, or 68.
Limitations of only 99 steps of keystrokes and has 3 built-in libraries (programs) that write over the existing 99 steps if loaded.
Still a best buy, even at retail list of $39. Often sells for more due to its recent discontinuation in 2003.
HP-27S
Perhaps HP's second best pocket calculator ever made, irrespective of RPN bigots (and overlooking the venerable 41c series). This was an algebraic only calculator.
BUT, it has 7 k RAM, a simple to use solver and a built in clock. And lots of functions all buried in menus but easy to get to and configure. This made for an ideal pocket calculator. This calculator was loaded with features and functions that made it useful for nearly any field.
HP-30S
Algebraic Kingpo made a calculator called the HP-30s. It has a fairly extensive scientific function set and is compariable to all other $10-20 calculators. It has switchable color faceplates and is stylish. Unfortunately, it doesn't compare in quality to the older HP-20 which it replaced. This cannot be expected as it is half the cost, but now there is no midrange quality programmable calculator available until you purchase the HP-33s at $50 or switch brands. It does have a crude solver and unit conversion and it has more functions than most other brands in this price range.
HP-42S
Simply the best pocket calculator available. Still has its drawbacks and doesn't quite measure up to a 41c series because it lacks I/O for program storage or control. Keyboard entry is the only way to imput programs at present.
Has lots of extra math functions over the 41c line, but lacks a clock also.
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