Currently open by appointment only, write Director@TheComputerChurch.org.

Think a Dot

YEAR: 1966
ITEM: Childrens' Comp./Game
COMPANY: E.S.R. Inc.
COUNTRY: USA
IN OUR COLLECTION: Yes

The Think-A-Dot was a mathematical toy made by E.S.R. Inc. in the 1960s. it had eight coloured disks on its front, and three holes on its top left, right, and center - through which a ball bearing could be dropped. Each disk would display either a yellow or blue face, depending on whether the mechanism behind it was tipped to the right or the left. The Think-a-Dot thus had 28=256 internal states. When the ball fell to the bottom it would exit either to a hole on the left or the right of the device.

As the ball passed through the Think-a-Dot, it would flip the disk mechanisms that it passed, and they in turn would determine whether the ball would be deflected to the left or to the right. Various puzzles and games were possible with the Think-a-Dot, such as flipping the colours of all cells in the minimum number of moves, or reaching a given state from a monochrome state or vice versa.

Get Our Newsletter  

Documents

Documents for this item have not yet been scanned or not yet posted. There are a lot of pages...contact us if you have an immediate need. (Although there are not a lot of "immediate needs" for a 70+ year old computer!)





If you know the location of any other of these items, please let us know by contacting us at Director@TheComputerChurch.com .

OUR DEFINITIONS OF RARITY

One of a Kind: Only known existing item.
Exceedingly Rare: Only 2 to 10 known to exist.
Very Rare: Only 11 to 25 are known to exist.
Rare: Only 26 to 50 are known to exist.
Difficult: Difficult to find.
Available:Can be commonly be purchased.
Unknown: We cannot make a determination.

(For comparison: Many people consider the Apple-1 computer to be rare. As of 2025 there are 92 confirmed and probable Apple-1 computers.)

We are still building. This feature will be ready by the end of February 2026.

(** indicates required entry)