In the computer, because "×" is easily confused with unknown X, it is not convenient to type, so * is used instead of multiplication sign.
In the set, if there is N*, it means the meaning of positive integer set, N*: positive integer set {1, 2,3, …}.
The set of positive integers is the set of all positive integers and integers, excluding 0 from the set of natural numbers until infinity. Positive integer sets usually use symbols N+, N*, N 1, N >；; 0 means.
The meaning of extended information * in the article
Asterisk * is usually placed in the upper left corner or upper right corner of related words, and takes up a single line when dividing different parts of the article as a symbol.
For example:
Qin Yuan Chun Xue (Modern Mao Zedong)
Look at what the northern countries have shown: a hundred miles of frozen Go; Thousands of miles of snow. Looking inside and outside the Great Wall, I only feel embarrassed; When the river rises and falls, it loses momentum. Mountain dancing silver snake, original wax elephant. *
......
* The original text refers to the plateau, namely the Qin Jin Plateau.
* Mountain dancing silver snake, original wax elephant. The mountains danced like silver snakes, and the hills on the plateau ran like many white elephants. Wax elephant, white elephant.
(Interpretation: The scenery in the north is frozen for thousands of miles, and the snow falls in Wan Li. Looking inside and outside the Great Wall, only a vast expanse of whiteness remains; The wide Yellow River suddenly lost its surging momentum.
The mountains are flying like silvery white pythons, and the hills on the plateau are running like many white elephants, all trying to compare with God. )