Vintage textbooks and calculators

The display is upside down probably because the calculator was subjected to a hacking procedure. Try to undo it or buy another calculator.

That is what you will get if your calculator is configured for the Line IO mode. If you want fractions to appear as in a textbook, you should configure your calculator's Input/Output mode to be MathIO. To do so press [SHIFT][MODE] to enter (SetUp) and select [1:MathIO]

Well, you cannot have them both at the same time. The calculator has two input/output modes: The MathIO and the LineIO (the old one). In MathIO you have textbook display. Expressions are entered and displayed as they appear in textbooks. In the LineIO mode expressions are entered on a single line (the old way).
You have to choose which one you want, because you cannot have them both enforced at the same time.

I suggest you use the natural display (textbook). After a result is displayed, you can press the [SD]
key and the result will be converted to a decimal number.
You can also press [SHIFT][=] instead of [=] to force the display to be in decimal format.

The I/YR key on the top row, with or without the shift key.

Typing 1 2 5 0 PV 1 5 2 0 +/- FV 4 N I/YR should give you 5.01

To convert a value to fractional form, use the >Frac function, accessible as the first item in the Math menu. Press MATH 1.

The Ti83/84PLUS are a lot more advanced than the TI-30XA because thaeu can graphs, statistics, calculus etc. But they lack a key for the % function, and a key for the fraction manipulation, the angle unit conversions (deg, radians, et grads) and they are a lot more expensive than the TI30XA.

Before your daughter finishes high school, you will eventually have to buy her a graphing calculator but right now a TI83/84Plus calculator seems like overkill. Besides some teachers may not let students have graphing calculators during exams.

Honestly I suggest you buy the TI-30XA Solar version. There are some new nifty calculators manufactured by Casio (Casio FX-115ES, FX-991ES, FX-300ES), Sharp (El-506W, 516W ). The beautiful thing about these new kinds of calculators is that you can configure them to use the Textbook display: equations and expressions can be entered as they would appear in textbooks. The Casios are called Natural Display and the Sharps are know as WriteView models.
In fairness to Texas Instruments, they too have calculators that incorporate that display format but I do not know the exact model numbers (maybe TI34XII multiview).

The calculator has two input/output (I/O) modes: MthIO and LineIO.
MthIO is a very nice novelty: it allows one to enter expressions as with pen and paper (textbook display). Results are displayed, whenever possible, as exact values ie fractions and radicals.
MthIO is the default I/O mode of the calculator. If it is not set, you can set it by pressing [SHIFT][MODE] (SetUp) to access a list of choices. Select [1:MthIO].

The other I/O mode is the old way of doing things: every thing is enter on the same level line, while in MthIO you have textbook style templates. In LineI/O all results are displayed as decimal (approximate) values.

To set LineIO press [SHIFT][MODE](SetUp) and select [2:LineIO].

If the displyed result is fresh you can toggle between decimals and fractions/radicals by pressing the [S<=>D] key.
Even if you are in MthIO you can force the (final) result into decimal display format by pressing, NOT the = sign, but [SHIFT][=] .

Hello,
If you use Mode [MathIO] the expressions are displayed as you will find them written in textbooks (Textbook display). You can readily see if that is what you had in mind.
To set MathIO press [Shift][Mode][1:MathIO]
Hope it helps.

Followed by a digit key, it probably set the display to fixed decimal notation with the specified number of digits following the decimal point.

No, it didn't magically fix a broken calculator :-)

You don't need a cpt button on Hp 10ii calculator.You can just press the function button that you want to apply without pressing cpt first.