First, multiply the number on each bit of the second factor by the first factor, from one digit to one digit. Then, add up the products. Several problems should be paid attention to in vertical calculation of multiplication: the last digit of two numbers should be aligned. Write the numbers with more numbers on it, and write the numbers with fewer numbers on it, so as to reduce the times of multiplication. If there is a "0" at the end of both numbers, the last digit of the number can only be aligned before the "0" when writing vertically, and finally the number "0" after the vertical product of the two numbers * * * is added.

The horizontal numbers are written compactly, and the vertical numbers are written separately. That is, when writing horizontally, the numbers should be written densely and not too far apart. When writing vertically, the numbers should be written separately because of counterpoint and carry. This is a habit that must be formed from the beginning.