How to make a punch-card computer

In this show we are going to make a punch-card computer out of stuff from your kitchen.

Most of the materials are things you would otherwise have thrown away.

What you will need

An empty breakfast cereal box.

Some bamboo barbecue skewers, eight for an eight bit computer, nine for a nine bit etc. These things come in cheap packs of many skewers. Or you could clean up used skewers.

Scissors or a sharp craft knife.

Some glue. Preferably washable PVA glue if you care about your clothes or have a small child 'helping'.

Some pieces of card which you can write on, the number corresponds to the 'bit-ness' of the computer. If you used eight skewers, you need eight bits of card. These need to be slightly narrower than the cereal box. They could be made from other cereal boxes sliced up. A height of about four inches, ten centimetres is good.

An enquiring mind and temporarily suspended credulity.

What to do

Step 1:

Prepare the case of the computer.

Cut off the box flaps at the top where the cereal was poured out.

The computer will eventually be used standing up in the usual position with the open end at the top.

Step 2:

Making a chute at the bottom.

You need to make a sort of chute at the bottom so that stuff that falls down into the box will slide out the front.

Do this by cutting a horizontal line across the width of the box about four or five inches, about eight centimetres from the bottom edge of the box.

Now cut down the front edges of the box from the horizontal slit to the bottom.

This will make a flap that you can fold down by putting your hand inside and pushing it out.

Hinge it down and make a fold in this flap about half an inch (one centimetre) from the front edge of the flap.

Coat the inside of the flap, above the fold, with glue. Now push the flap back up and press the folded (gluey) portion of the flap against the inside of the back of the box. You could use some sticky tape to hold it down while it dries.

When the glue has dried you will be able to see how this now forms a chute at the bottom of the box.

Step 3:

Now draw a horizontal line across the front side of the box about an inch, or 2.5 centimetres from the open end.

Now is the trickiest part because you will need to do some arithmetic. Pity you don't have a computer, right?

You need to measure out a number of points across this line which correspond to the bit-ness of your computer. So if you are making an eight bit computer, you need eight marks spaced equally across this line, that's nine gaps across.

When you have done this you are going to pierce holes in the box with either one of the BBQ skewers or something sharper. You need for the skewers to pass right through the box and out the back side, in the same position as accurately as possible. This might be easier if you draw and measure out the same points on the back panel and push holes through from both sides.

Either way what you are aiming for is to make the path through the box as accurately level and equi-distant as possible. The skewers should pass through the box and remain parallel.

Step 4:

We are now going to make the punched cards.

Create the same number of cards as the bit-ness of your computer. So an eight bit computer will require eight cards.

The cards will be almost as wide as the inside of the box, and tall enough to write stuff on but not high enough to show their bottom edges through the chute hole at the bottom of the computer. And not so tall that when they fall to the bottom they get wedged between the chute and the back wall of the computer.

Laying each card flat on the table, draw a horizontal line across the card about

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