These were the abacus, Napier's bones, Oughtred's Slide, Pascal's calculator, Leibniz's calculator. These were the earliest computing devices, and were used in early history to make efficient calculations.

• The Abacus first appeared in 2700-2300 BC in Mesopotamia; it was first designed with successive columns with successive orders of magnitude. Beans or stones were moved along in sand or tablets of stone in some forms. Other forms were designed in Egypt, Persia, Greece, Rome, China, India, Japan, Korea, Native America, and Russia. It was used for centuries prior to the development of the modern numeric system.

• Napier's bones was a type of abacus designed by John Napier based on lattice multiplication and Arab mathematics. He used multiplication tables embedded in the rods, although these could also be used for addition, division, and subtraction calculations.

• Pascal's calculator was invented by Blaise Pascal in 1642, which proved to be an efficient early device for direct subtraction, multiplication, and repetitive division. He discovered the machine while trying to think of a device to help his father in tax calculations in France, and had to go through 50 prototypes before the first machine was presented to the public. Blaise Pascal created about twenty more prototypes over the following decade, all of which were constant improvements of the last model. Pascal's calculator paved the way for the introduction of the first mechanical calculators in Europe and the rest of the world.

• The Leibnitz's calculator was a mechanical device created out of copper and steel, designed to multiply, divide, add, and subtract. Wheels were designed on right angles which could be manually displaced by a special stepping mechanism to perform various operations. In order to successfully use this type of calculator, the operator had to know how to turn the wheels properly and perform the calculations.

These early forms of computing have come a long way and have formed the foundations of important calculating devices we use today.

• The Abacus first appeared in 2700-2300 BC in Mesopotamia; it was first designed with successive columns with successive orders of magnitude. Beans or stones were moved along in sand or tablets of stone in some forms. Other forms were designed in Egypt, Persia, Greece, Rome, China, India, Japan, Korea, Native America, and Russia. It was used for centuries prior to the development of the modern numeric system.

• Napier's bones was a type of abacus designed by John Napier based on lattice multiplication and Arab mathematics. He used multiplication tables embedded in the rods, although these could also be used for addition, division, and subtraction calculations.

• Pascal's calculator was invented by Blaise Pascal in 1642, which proved to be an efficient early device for direct subtraction, multiplication, and repetitive division. He discovered the machine while trying to think of a device to help his father in tax calculations in France, and had to go through 50 prototypes before the first machine was presented to the public. Blaise Pascal created about twenty more prototypes over the following decade, all of which were constant improvements of the last model. Pascal's calculator paved the way for the introduction of the first mechanical calculators in Europe and the rest of the world.

• The Leibnitz's calculator was a mechanical device created out of copper and steel, designed to multiply, divide, add, and subtract. Wheels were designed on right angles which could be manually displaced by a special stepping mechanism to perform various operations. In order to successfully use this type of calculator, the operator had to know how to turn the wheels properly and perform the calculations.

These early forms of computing have come a long way and have formed the foundations of important calculating devices we use today.