Posting letters
Nick Cook, School of Computing Science, Newcastle University
http://www.ncl.ac.uk/computing/outreach/resources/primary
Preamble
In this activity we look at input, storage and output of letters (characters) in
computing. We can use this activity to look at computer storage and how a
computer knows that a letter (or character) has been input. The activity can also
be used simply to write words and/or send messages. Output in this example is
to a whiteboard. It could be output by some other means (e.g. voice).
Activity
Resources
 A set of letter cards
 Three numbered post boxes - boxes with lids, slots to post cards through
and a flag to show that the box has something in it. The boxes are
numbered 1 to 3.
 5 players – 1 writer, 3 postal workers, 1 shopkeeper at the post office
counter
 Instructions for the message writer, three post workers, and the shop
keeper at the Post Office counter
The boxes are arranged as follows, with flags down to start:
writer
1
shopkeeper
2
3
Workshop worksheet (po1)
What is the "computer" doing?
What is the longest word this "computer" can store at a time?
What if we only have one box, can we still write a word? How?
Which instructions would we use? Can we still have more than one post worker?
Why is it useful to have more than one box?
What happens if there are no flags on the post boxes?
What happens if someone forgets to put a flag up or down?
What happens if the shopkeeper (or someone else) goes for a coffee?
How can we use this computer to write sentences?
How can we use this computer to send and receive messages?
What extensions/changes do we need?
Please discuss the suitability of this activity, improvements and extensions. For
example:
 Is the level appropriate to Key Stage 1 and which year?
 Are there changes you would suggest?
 Are there links to or uses in other parts of the Key Stage 1 curriculum?
 Are there links to your own practice?
Instructions for the writer
 Think of a three-letter word.
 Use the letter cards to spell the word out
on the table
 When the flag on the post box in front of
you is down, starting with the first letter:
1. Post the next letter card in your word in
the post box
2. Put the flag up on the post box
Instructions for Postman Pat
When the flag on post box 3 is up
and
the flag on post box 2 is down:
1. Open the lid of post box 3
2. Take the card out of post box 3
3. Close the lid of post box 3
4. Put the flag down on post box 3
5. Post the card in post box 2
6. Put the flag up on post box 2
Instructions for Postwoman Pat
When the flag on post box 2 is up
and
the flag on post box 1 is down:
1. Open the lid of post box 2
2. Take the card out of post box 2
3. Close the lid of post box 2
4. Put the flag down on post box 2
5. Post the card in post box 1
6. Put the flag up on post box 1
Instructions for the Black and
White Cat
When the flag on post box 1 is up:
1. Open the lid of post box 1
2. Take the card out of post box 1
3. Close the lid of post box 1
4. Put the flag down on post box 1
5. Take the card to the shopkeeper at the
Post Office counter. If the shopkeeper
is busy, wait for them to take the card.
Instructions for the shopkeeper
Write any letter you are given on the
whiteboard, one after the other, left to right.