HP 35s HP 35s scientific calculator - User Guide - Page 61

4 ÷ [14 + (7 × 3) - 2] by starting with the innermost parentheses (7 × 3) and working outward, just as you would with pencil and paper. The keystrokes were If you work the problem from left-to-right, press This method takes one additional keystroke. Notice that the first intermediate result is still the innermost parentheses (7 × 3). The advantage to working a problem left-to- right is that you don't have to use  to reposition operands for noncommutative functions (  and  ). However, the first method (starting with the innermost parentheses) is often preferred because: It takes fewer keystrokes. It requires fewer registers in the stack. Note When using the left-to-right method, be sure that no more than four intermediate numbers (or results) will be needed at one time (the stack can hold no more than four numbers). The above example, when solved left-to-right, needed all registers in the stack at one point: Keys:   Display _ Description: Saves 4 and 14 as intermediate numbers in the stack. At this point the stack is full with numbers for this calculation. Intermediate result. Intermediate result. RPN: The Automatic Memory Stack 2-15