变量是什么What Are Variables?

3.1 变量就像一个盒子3.1 A Variable Is Like a Box

想象你有一个盒子，盒子上贴了一个标签写着"年龄"。你可以往盒子里放一个数字，比如 14。Imagine you have a box with a label that says "age." You can put a number in it, like 14.

以后你想知道年龄是多少，就看看盒子里的东西。你也可以把 14 拿出来，换成 15 -- 盒子还是那个盒子，标签没变，但里面的东西变了。Later, when you want to know the age, just look inside the box. You can also take out 14 and replace it with 15 — the box is the same, the label hasn't changed, but the content inside has.

3.2 声明一个变量3.2 Declaring a Variable

在 C++ 里，创建（声明）一个变量需要三样东西：类型、名字、初始值。In C++, creating (declaring) a variable requires three things: a type, a name, and an initial value.

int age = 14;          // 整数：年龄是 14
double speed = 3.5;    // 小数：速度是 3.5
const char* name = "VEX";  // 文字：名字是 VEX

分解来看：Breaking it down:

• int — 类型，表示这个盒子只能放整数int — The type, meaning this box can only hold whole numbers
• age — 名字，你给这个盒子贴的标签age — The name, the label you put on the box
• = 14 — 初始值，一开始放进去的东西= 14 — The initial value, what you put inside at the start
• ; — 分号，每行代码的结尾都要加; — Semicolon, required at the end of every line of code

3.3 三种常用类型3.3 Three Common Types

3.4 变量可以改3.4 Variables Can Change

变量之所以叫"变量"，就是因为它的值可以变。Variables are called "variables" because their values can change.

int age = 14;    // 一开始是 14
age = 15;        // 现在变成 15 了
age = age + 1;   // 在当前值的基础上加 1，变成 16

注意：改变量的值时，不用再写类型（不用再写 int）。类型只在第一次声明时写一次。Note: When changing a variable's value, you don't write the type again (no need to write int again). The type is only written once when you first declare it.

3.5 把变量显示在屏幕上3.5 Display Variables on the Screen

我们可以把变量的值打印到 Brain 屏幕上：We can print a variable's value to the Brain screen:

int main() {
    int score = 88;
    Brain.Screen.print("Score: %d", score);
    return 0;
}

int main() {
    int score = 88;
    Brain.Screen.print("Score: %d", score);
    return 0;
}

void initialize() {
    pros::lcd::initialize();
    int score = 88;
    pros::lcd::print(1, "Score: %d", score);
}

int x = 5;
x = x + 3;

3.6 写代码练习3.6 Coding Exercise

int main() {
    int laps = 0;
    laps = laps + 1;
    laps = laps + 1;
    Brain.Screen.print("Laps: %d", laps);
    return 0;
}

int main() {
    int laps = 0;
    laps = laps + 1;
    laps = laps + 1;
    Brain.Screen.print("Laps: %d", laps);
    return 0;
}

void initialize() {
    pros::lcd::initialize();
    int laps = 0;
    laps = laps + 1;
    laps = laps + 1;
    pros::lcd::print(1, "Laps: %d", laps);
}