1. vertical addition: align two three-digit numbers, add them bit by bit from one digit, and add 1 to the last digit in the case of carry, and finally get the result.

2. Vertical subtraction: the minuend is aligned with the subtree, and subtraction is done bit by bit from the unit. If the minuend is smaller than the subtree, the result is obtained by borrowing from a higher position.

Data expansion:

Vertical calculation refers to a vertical calculation in the calculation process, which makes the calculation simple. In addition calculation, the same numbers are aligned. If the sum exceeds 10, it will move forward to 1. When subtracting, the same numbers are aligned. If it is not enough, borrow 1 from the last digit as 10.

Arabic numerals:

Arabic numerals (also called Indian numerals) consist of ten counting symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 * *. Arabic numerals were first invented by ancient Indians, then spread to Europe by Arabs, and then modernized by Europeans. People think it was invented by Arabs, so people call it "Arabic numerals".

Indian figures:

In the 3rd century AD, the ancient Indian scientist Baghdad invented Arabic numerals. The oldest meter is about 3 meters. In order to imagine the number "4", it is necessary to add 2 and 2. 5 is 2 plus 2 plus 1, and 3 is 2 plus 1. Handwriting with five fingers for the number 5 and hands with ten fingers for the number 10, which is probably too late. This principle is actually the basis of mathematical calculation.

Rome's count is only numbers within V (that is, 5), and numbers within X (that is, 10) are composed of V (5) and other numbers. ⅹ is a combination of two ⅴ, and the same digital symbol has different quantities according to its position relationship with other digital symbols.

In this way, the concept of digital position began, and this important contribution in mathematics should be attributed to the ancient residents of the two river basins. Later, the ancients improved on this basis and invented nine symbols 1, 2, 3, 4, 5, 6, 7, 8 and 9 to represent numbers.

It was not until the 9th century AD, that is, in 876 AD, that the concept of 0 was recorded for the first time on the stone tablet of Gualil unearthed in India. The meaning of zero is deeply influenced by Mahayana Buddhism in India: 0 multiplied by any number will be 0, and the concept is that everything is empty. Therefore, 0 is considered as the starting point of numbers, and the invention of 0 is of great significance in the history of mathematical development.