1, integer length

Integer and Long are both integers. After the user defines a variable as an integer variable, only integers can be assigned to the variable. Integers have a certain range from -32768 to 32767. If it goes beyond this range, use a dragon.

2. Real numbers (single and double)

Single-precision and double-precision numerical values are floating-point numerical values, and real numbers are expressed by decimals. Single precision can be accurate to seven digits, and double precision can be accurate to 15 digits. When choosing these data types, users should pay attention to the range of variables. When the numerical value is an integer, it is not necessary to define the variable as a floating-point type for the sake of operation speed. For large floating-point numbers, you can use d.