HP 35s HP 35s scientific calculator - User Guide - Page 34

Performing Arithmetic Calculations The HP 35s can operate in either RPN mode or in Algebraic mode (ALG). These modes affect how expressions are entered. The following sections illustrate the entry differences for single argument (or unary) and two argument (or binary) operations. Single Argument or Unary Operations Some of the numerical operations of the HP 35s require a single number for input, such as and k. These single argument operations are entered differently, depending on whether the calculator is in RPN or ALG mode. In RPN mode, the number is entered first and then the operation is applied. If the  key is pressed after the number is entered, then the number appears in line 1 and the result is shown in line 2. Otherwise, just the result is displayed in line 2 and line 1 is unchanged. In ALG mode, the operator is pressed first and the display shows the function, followed by a set of parentheses. The number is entered between the parentheses and then the  key is pressed. The expression is displayed in line 1 and the result is shown in line 2. The following examples illustrate the differences. 1-18 Getting Started