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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 

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 
Associated Topics:
High School Calculators, Computers

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