上一片，小电脑给数据上了锁。可主人开了校园小卖部，订单多到记不住。这一片，给每个数据起个名字。Last leaf, the little computer locked data up. Now its owner opens a campus snack stand, with too many orders to remember. This leaf gives every datum a name.
第 1 步：盒子贴上标签Step 1: A box with a name tag
数据太多记不住，怎么办？Too many values to remember — what helps?
变量就是贴标签的盒子。名字写外面，比如 total。值放里面，比如 5。赋值就是“放进去”：total = 5。喊名字，盒子就张嘴。A variable is a labeled box. The name sits outside, like total. The value sits inside, like 5. Assigning means “put it in”: total = 5. Call the name, the box opens.
放进去的东西，能换吗？Once inside, can the value change?
第 2 步：改值不变名Step 2: New value, same name
能！购物车总额 total 先是 35。再买两样，变成 48。名字还是 total。程序里处处是变量：分数、余额、步数。Yes! The cart total starts at 35. Two more snacks make it 48. The name total never changes. Code is full of variables: scores, balances, step counts.
盒子里只能装数字吗？Can a box hold only numbers?
第 3 步：三种盒子Step 3: Three kinds of boxes
不只！数字盒装 7。文字盒装“你好”。真假盒只装开或关。小电脑按种类干活。装错种类，会闹笑话。Not only numbers! A number box holds 7. A text box holds “hi”. A true/false box holds only on or off. The little computer works by kind. Mix up kinds, and results get silly.
🎮 你来当店长（30 秒）🎮 Your turn: be the shopkeeper (30 seconds)
道理讲完了。先亲手往盒子里放几个值，再接 4 关：猜猜盒子里最后是多少。Theory done. First put a few values in the box yourself, then take 4 rounds: guess what ends up inside.
一句话记住它：变量 = 有名字的数据盒子；赋值是放进去，改值不变名。Remember it in one line: a variable = a named box for data; assigning puts a value in, and the name stays while values change.
赋值就是放进去：total = 5Assigning puts it in: total = 5改值不变名：总额 35 → 48Value changes, name stays: total 35 → 48三种常用盒子：数字 / 文字 / 真假Three everyday boxes: number / text / true-false
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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