The first Mechanical calculator
Blaise Pascal was also the inventor of the mechanical calculator. His first calculator could only do addition and subtraction but it was still very successful. Although his calculator did not sell well it still had a big impact on future calculators. Blaise Pascal revised and invented about 20 different versions of new and improved calculators. Blaises calculator though big and very bulky was very useful at the time of its invention and that's why it was so expensive.