1 integer, including short, int, long, long long, etc. , which is used to represent an integer, is signed by default, and can be expressed as unsigned with the unsigned keyword.

2 Real numbers, that is, floating points, including float and double, are used to represent real numbers. Compared with integer type, this type can represent numerical values with decimal parts. It should be noted that the real type is an approximate representation in computer language, not an accurate value, and the deviation of the true value may occur after many calculations.

3-character type, that is, char type, is used to represent various characters and corresponds to ascii code table one by one. Except that it can be used to represent various characters, other rules of char type are the same as those of integer, and char can be considered as a special integer.