# The tsc Compiler

Let's set up a simple TypeScript Node.js application on your local machine. Follow these steps to get started:

**Step 1 - Install `tsc`/TypeScript Globally**

First, install TypeScript globally using npm.

```bash
npm install -g typescript
```

**Step 2 - Initialize a Node.js Project with TypeScript**

Create a new directory for your Node.js application and initialize it with TypeScript.

```bash
mkdir node-app
cd node-app
npm init -y
npx tsc --init
```

These commands will create your project directory and initialize it with `package.json` and `tsconfig.json`.

**Step 3 - Create a `a.ts` File**

Create a new TypeScript file named `a.ts` and add the following code:

```typescript
const x: number = 1;
console.log(x);
```

**Step 4 - Compile the `.ts` File to a `.js` File**

Use the TypeScript compiler to compile your TypeScript file into JavaScript.

```bash
tsc -b
```

**Step 5 - Check the Generated `a.js` File**

Open the generated `a.js` file. You'll see that it contains plain JavaScript code with no type annotations.

```javascript
var x = 1;
console.log(x);
```

**Step 6 - Modify `a.ts` to Assign `x` to a String**

Change `a.ts` by converting `const` to `let` and assigning `x` to a string:

```typescript
let x: number = 1;
x = "something other than number";  // This will cause a type error
console.log(x);
```

**Step 7 - Recompile the Code**

Compile the code again with the TypeScript compiler:

```bash
tsc -b
```

You will see errors in the console indicating type mismatches. Additionally, notice that no `a.js` file is generated this time due to the type errors.