Front

Earliest computing device

Back

the abacus

Front

Abacus invention

Back

Mesopotamia, 2500 BCE

Front

Number shown on the abacus?

Back

1,251

Front

Device for calculating latitude at sea

Back

Astrolabe

Front

Earliest documented use of 'computer'

Back

1613

Front

Early definition of "computer"

Back

A person who did calculations

Front

Gear-based calculating device by Leibniz (1694)

Back

The step reckoner

Front

Step Reckoner usage duration

Back

Next three centuries

Front

Computing before the 20th century

Back

Pre-computed tables

Front

First military application of computing

Back

Calculating range tables