Previous Value
Previous Value
77
77
Figure 5 Duplicating a Number on the Stack
In RPN, the parentheses keys (Dmanipulate the stack. Pressing (performs a roll
down of the stack. A roll down causes the stack to roll towards the bottom of the stack, during which the number in Level 2 to moves down to Level 1, the number in Level 3 to moves down to Level 2, the number in Level 4 to moves down to Level 3, and the number of Level 1 to moves
up to Level 4. The (key has a small down arrow on it to indicate the roll down feature.
With the numbers entered into the stack shown in the left column in Figure 6, pressing ( performs the roll down of the stack shown in the right column.
12-15
4112
2341
Figure 6 The RPN Stack and the Roll Down Operation
Mathematical Calculations 17