Although HP CALC's display seems complicated at first glance, using HP CALC as a regular calculator is quite easy. Start the application and you see a blank screen with the Words "Calculator Arithmetic" at the top. Type in any number (i.e. "555") and the number appears down in the bottom right-hand corner of the screen, below a long horizontal line. This is where the numbers you enter and answers you receive will appear. Now press the keypads plus sign (+), type in 555 again, and press the equal sigh (=). The answer, 1110, appears at the bottom right. It's that simple.
The 95LX keypad is almost identical to a standard calculator's keypad. The division (/), multiplication (*), subtraction (-), addition (+), and equals (=) keys are on the right of the keypad, just like a regular calculator. You use them just like you would on a regular calculator. The memory (M), memory recall (RM), memory plus (M+), and memory minus (M-) keys are (F7), (F8), (F9), and (F10) respectively. The (DEL) works like the clear key on your calculator.
But HP CALC is more than a regular calculator. The "(" and ")" on your keypad allows you to use brackets in an algebra-like manner. The exponent (^) and percentage (%) work as expected in Calculator Arithmetic, and the Z, X, C, V, B, N, M, and L keys activate other calculator functions.
But what about the rest of the HP CALC display. Why all that space? Press (F2) (SHOW) and you'll see the following screen. Graphic
Reg0(M) through Reg4 at the top are "memory registers", locations where you can store numbers and results of calculations. The bottom "Stacks" show the results of your last three calculations. (Stack (1) in the above screen shows that the results of the last calculation was 1,110.00. The "6.00+" at the bottom indicates that you are in the middle of a new addition.)
If you press (F2) again you will see that you actually have 10 memory registers (Reg0(M) through Reg9). To store the displayed number in a specific register, press (N) (STO) followed by the register number. To recall a value from a register, press (M) (RCL), followed by the register number.
This should get you up and going on HP CALC. For more on HP CALC, see the HP 95LX Users Guide, beginning on page 22-2.