How is an em dash formed in writing?

The em dash is created by typing two hyphens in a row. This method, often used in plain text environments where special characters might not be readily available, successfully emulates the longer dash that is used for various grammatical purposes, such as setting off information for emphasis or interrupting a thought. In word processing software, the program may automatically convert two hyphens into an em dash when the text is typographically rendered.

While typing a single hyphen creates a regular hyphen and using a long dash key (if available) could be an effective method in certain applications, they do not produce an em dash. Typing a combination of letters would not yield an em dash as it lacks the specific character structure needed for it. Therefore, using two hyphens to generate an em dash is a widely accepted practice in writing, especially in text-based environments.