Many people want to credit Blaise Pascal with the creation of the adding machine. That is only partially correct.
The first adding machine was created in 1623 by Wilhelm Schickard. Unfortunately, the machine was destroyed by a fire. Knowledge of the machine comes from letters that Wilhelm Schickard wrote to Johannes Kepler, credited with the creation of eponymous laws of planetary motion. The letters were only found years after the death of Kepler and some university students have tried to recreate the machine. The machine was known as a speeding clock or a calculating clock and could add numbers up to six digits. The speeding clock was used to make complex calculation in the creation of astronomical tables. The machine was never completed.
Twenty years after the creation of this first adding machine Blaise Pascal created the first finished adding machine. Blaise created the machine to help his Dad collect taxes for the French government. He knew how hard his Dad worked and as an eighteen year old wanted to help his Dad. The machine was known as a numerical wheel calculator or pascaline and could only be used to add and subtract. It used a train of eight moveable dials. This machine was never widely sold. Blaise Pascal went on to create many other inventions, which proved more successful.