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### What is a Keystroke Sequence?

```Date: 07/30/2002 at 13:33:35
From: Charice
Subject: Keystroke sequence

What is a 'keystroke sequence'?  It is used in the following question:

Write out the keystroke sequence required to calculate
8/[3^4-(-4-3)].

My husband is doing a math placement exercise, and neither of us is
sure how to begin solving this problem.  Thanks!
```

```
Date: 07/30/2002 at 18:02:51
From: Doctor Ian
Subject: Re: Keystroke sequence

Hi Charice,

A keystroke sequence is the sequence of keys that you would punch on a
particular calculator to find the value of some expression. Note that
for a given expression, the proper keystroke sequence will differ from
calculator to calculator.

Think of it this way. Suppose you're on the phone with someone who has
a calculator, and you want him to work out the value of an expression
for you, but he doesn't understand math at all.  You have to tell him
what keys to press, in what order, e.g., to compute 3/(2 + 4) you'd
have to say something like this:

Press '2'
Press '+'
Press '4'
Press '='
Press 'STO'     (store this result)
Press '3'
Press '/'
Press 'RCL'     (recall the previously stored result)
Press '='
Tell me what you see.

In this case, the keystroke sequence would be

'2', '+', '4', '=', 'STO', '3', '/', 'RCL', '='

On a different calculator (one with parentheses), it might be

'3', '/', '(', '2', '+', '4', ')', '='

On a calculator that uses Reverse Polish Notation, the keystroke
sequence would be

'3',  '2',  '4',  '+', '/'

(In this case, the '/' says "Of the two most recent operands, divide
the first by the second"; but when the second operand turns out to be
an operator, the '+' says "Of the two most recent operands, add the
first to the second."  When that operation is done, it becomes the
second operand for the first operation. If this doesn't make sense to
you, make sure not to buy this kind of calculator!)

Does this help?

- Doctor Ian, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
High School Calculators, Computers

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