Calculator input methods: Difference between revisions

Revision as of 13:52, 4 May 2009

Revision as of 13:52, 4 May 2009

Line 5:

There are various ways in which the in which a button-operated calculator might interpret key strokes.

=== Immediate execution ===

=== Reverse Polish Notation (RPN) (Postfix notation) ===

With this mode of operation each [[binary operation]] is executed as soon as the next operator is pressed, therefore the order of operations in a mathematical expression is not taken into account. Some calculators have buttons for brackets and these calculators ''can'' take order in to account. Also for [[unitary operators]] like √ or x² the number is entered first then the operator.

{{main|Reverse Polish Notation}}

In Reverse Polish Notation also known as '''Postfix notation''' all operations are entered after the [[operand]]s on which the operation is performed. Reverse Polish Notation is parenthesis-free which usually leads to less button presses needed to perform a operation. By the use of [[Stack_(data_structure)|stack]] one can enter formulas without the need to rearrange operands.

{| class="wikitable" border="1"

Line 18 ⟶ 16:

|-

| <math>1 + 2 \times 3</math>

| <code>12</code> <code>ENTER×</code> <code>23</code> <code>ENTER+</code> <code>31</code> <code>×</code> <code>+=</code>

| 76

|-

| <math>\sin 30 \times \cos 30</math>

| <code>3</code> <code>0</code> <code>SIN</code> <code>×</code> <code>3</code> <code>0</code> <code>COS</code> <code>×=</code>

| 78

|}

From the first example one can see that it is necessary to rearrange operands in order to get the correct result.

Note example 1 which is one of the few examples where Reverse Polish Notation does not use the fewest button presses - provided one does not rearrange operands. If one would do so then only 5 key strokes would be needed.

=== Reverse Polish Notation (RPN) (Postfix notation) ===

=== Immediate execution ===

{{main|Reverse Polish Notation}}

With this mode of operation each [[binary operation]] is executed as soon as the next operator is pressed, therefore the order of operations in a mathematical expression is not taken into account. Some calculators have buttons for brackets and these calculators ''can'' take order in to account. Also for [[unitary operators]] like √ or x² the number is entered first then the operator.

In Reverse Polish Notation also known as '''Postfix notation''' all operations are entered after the [[operand]]s on which the operation is performed. Reverse Polish Notation is parenthesis-free which usually leads to less button presses needed to perform a operation. By the use of [[Stack_(data_structure)|stack]] one can enter formulas without the need to rearrange operands.

{| class="wikitable" border="1"

Line 39:

|-

| <math>1 + 2 \times 3</math>

| <code>21</code> <code>×ENTER</code> <code>32</code> <code>+ENTER</code> <code>13</code> <code>=×</code> <code>+</code>

| 67

|-

| <math>\sin 30 \times \cos 30</math>

| <code>3</code> <code>0</code> <code>SIN</code> <code>×</code> <code>3</code> <code>0</code> <code>COS</code> <code>=×</code>

| 87

|}

Note example 1 which is one of the few examples where Reverse Polish Notation does not use the fewest button presses - provided one does not rearrange operands. If one would do so then only 5 key strokes would be needed.

From the first example one can see that it is necessary to rearrange operands in order to get the correct result.

=== Infix notation ===