How do I set a CSS class to all the components of an application?

Setting a CSS class for all components in an application depends on the framework or library you're using. Below, I'll provide examples for different popular frameworks.

 Angular:

In Angular, you can apply a CSS class globally by adding it to the `styles.css` or `styles.scss` file in your project. Any styles defined in this file will be applied globally to your entire application.

```css
/* styles.css or styles.scss */
.my-global-class {
  color: red;
  /* Add any other global styles */
}
```

 React:

In React, you can use a CSS file and import it into your main component or use a CSS-in-JS solution like styled-components.

1. **Using a CSS File:**

Create a CSS file (e.g., `styles.css`) and define your global styles.

```css
/* styles.css */
.my-global-class {
  color: red;
  /* Add any other global styles */
}
```

Import the CSS file in your main component or entry file.

```jsx
// App.js or index.js
import React from 'react';
import './styles.css';

function App() {
  return (
    <div className="my-global-class">
      {/* Your app content */}
    </div>
  );
}

export default App;
```

2. **Using styled-components:**

Install `styled-components` if you haven't already:

```bash
npm install styled-components
```

Define your global styles using `createGlobalStyle`.

```jsx
// GlobalStyles.js
import { createGlobalStyle } from 'styled-components';

const GlobalStyles = createGlobalStyle`
  .my-global-class {
    color: red;
    /* Add any other global styles */
  }
`;

export default GlobalStyles;
```

Import `GlobalStyles` in your main component or entry file.

```jsx
// App.js or index.js
import React from 'react';
import GlobalStyles from './GlobalStyles';

function App() {
  return (
    <>
      <GlobalStyles />
      <div className="my-global-class">
        {/* Your app content */}
      </div>
    </>
  );
}

export default App;
```

### Vue.js:

In Vue.js, you can use a global stylesheet by importing it in your main entry file (e.g., `main.js`).

1. **Create a CSS File:**

```css
/* styles.css */
.my-global-class {
  color: red;
  /* Add any other global styles */
}
```

2. **Import in main.js:**

```javascript
// main.js
import Vue from 'vue';
import App from './App.vue';
import './styles.css'; // Import the global stylesheet

Vue.config.productionTip = false;

new Vue({
  render: h => h(App),
}).$mount('#app');
```

In summary, the approach depends on the specific framework you are using. Generally, adding a global CSS class involves defining the styles in a file and making sure it is imported or included at a global level in your application.