Columns dialog box can be opened from:
1. Format menu Columns submenu: The Columns dialog box can be accessed from the Format menu in various software applications, such as Microsoft Word. To open it, you need to follow these steps:
- Click on the "Format" menu located at the top of the application window.
- A drop-down menu will appear.
- Look for the "Columns" option in the menu and click on it.
- This will open the Columns dialog box, where you can customize the column settings for your document.

2. Double click on column space in ruler: Another way to open the Columns dialog box is by double-clicking on the column space in the ruler. The ruler is a horizontal bar that appears at the top of the document window in applications like Microsoft Word. To open the Columns dialog box using this method, follow these steps:
- Locate the ruler at the top of the document window.
- In the area of the ruler where the columns are displayed, double-click on the empty space between the column markers.
- This will open the Columns dialog box, allowing you to modify the column settings.

3. Press Alt + O + C: In some software applications, you can use keyboard shortcuts to access different options and features. To open the Columns dialog box using the keyboard shortcut, follow these steps:
- Press and hold the "Alt" key on your keyboard.
- While holding the "Alt" key, press the letter "O" and then the letter "C" on your keyboard.
- This keyboard shortcut combination will open the Columns dialog box.

Summary:
The Columns dialog box can be opened from multiple locations, including the Format menu, the ruler, and by using keyboard shortcuts. These methods provide different ways to access the Columns dialog box, allowing users to customize and adjust the column settings for their documents.