reference link: https://www.runoob.com/cprogramming/c-variables.html
Types of C variables
| type | description |
|---|---|
| char | 通常为一个字节（八位），这是一个整数类型 |
| int | 整型，4 字节 |
| float | 单精度浮点值 |
| double | 双精度 |
| void | 表示类型的缺失 |
Definition of C variables
Such as int, char, float, double
Those things are connected to Place holder when you want to output some things.