In HP Calc the Z, X, C, V, B, N, M and L keys perform the various functions printed in white below them. Here is a list of these key definitions and what they do.
(Z) (square root symbol) --Calculates the square root of the number in the calculation line. For example, if you enter 16 in the calc line and press (Z), the calc line displays the square root of 16 (4).
(X) (1/x) --Calculates the reciprocal of the number in the calc line. For example, if you enter 4 in the calc line, then press (X), the calc line displays .25.
(C) (x><y) --Exchanges the numbers in the X and Y registers, if you're using the RPN mode. If you're using the algebraic mode and the calc line contains an expression like 3/4, the C key will swap the numbers on either side of the operator, e.g., 4/3.
(V) (R +DownArrow) --Rolls the number from register #1 (register Y in RPN) into the calc line and puts the calc line number into register #4 (register T in RPN).
(B) (LAST) --In algebraic mode, this key copies the result of the previous calculation into the current calculation: in RPN it copies the value that was in the X register, just before a calculation, back into the X register (the calc line.)
(N) (STO) --Stores the number in the calc line to a designated memory register (i.e., stores the number in the calc line to a number key you designate). E.g., if you enter 3,452.78 in the calc line and press (N)(STO) 3, the number 3,452.78 is stored in the memory register #3.
(M) (RCL) --Recalls a number you stored previously (when you pressed (N)(STO)) from the register in which you stored it.
(L) (+/-) --Makes a positive number negative or a negative number positive. For example, if you press (+/-) while the number 118 is in the calc line, it changes it to -118. Pressing (+/-) a second time makes the number positive again. If you want to enter a number in scientific notation, e.g., 5.5 E-3, type 5.5 e 3 L. You'll see 5.5e-3 and when you press Enter you'll see 0.0055.
NOTE: There is no key for X^2 (X squared). As a "workaround" for this missing key, put HP Calc in RPN mode, and key in a number, press Enter and press * (times).