What is a file extension?

• A. The period in a filename
• B. The suffix at the end of a filename that indicates what type of file it is
• C. The main part of a file's content
• D. The title of the file

Answer: (B)

A file extension is the suffix at the end of a filename that indicates the type of file it is. This suffix typically consists of three to four characters, following a period, and helps the operating system and users identify the file format. For example, a file named "document.txt" uses the ".txt" extension, which signifies that it is a plain text file. Similarly, other extensions like ".jpg" indicate an image file, and ".docx" signifies a Microsoft Word document.

Recognizing file extensions is crucial for understanding how to open a file properly or which programs can be used to view and edit that file. The function of a file extension is vital for file management and organization within computer systems, ensuring that users can differentiate between files and understand their specific capabilities based on their formats.