File formats and extensions in Intro to Computing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a file extension?

A file extension is the set of letters after the last dot in a file name. It tells the computer what type of file it is, like .txt for text files or .jpg for images.

beginner

Why do computers use file formats?

File formats organize data in a specific way so programs know how to open and read the file. For example, a .mp3 file stores music in a way music players understand.

beginner

Match the file extension to its type:
1. .pdf
2. .mp4
3. .docx
4. .png

1. PDF document
2. Video file
3. Word document
4. Image file (Portable Network Graphics)

intermediate

What happens if you change a file's extension incorrectly?

Changing a file's extension wrongly can confuse the computer. It might try to open the file with the wrong program, causing errors or the file not opening at all.

intermediate

Explain the difference between a file format and a file extension.

A file format is the way data is stored inside the file. The file extension is the label at the end of the file name that hints at the format. For example, .txt is the extension, and plain text is the format.

What does the file extension '.jpg' usually indicate?

A An image file

B A text document

C A video file

D A spreadsheet

The '.jpg' extension is commonly used for image files, especially photos.

Which file extension is commonly used for audio files?

A .exe

B .mp3

C .pdf

D .docx

'.mp3' is a popular file extension for audio files.

If you rename a '.txt' file to '.jpg', what is likely to happen?

A The file will open as an image but show gibberish or error

B The file will become a picture

C The file will delete itself

D Nothing will change

Changing the extension does not change the file content. The computer tries to open it as an image but fails.

Which of these is NOT a file extension?

A .exe

B .html

C .zip

D .folder

'.folder' is not a standard file extension; folders are directories, not files.

What does a PDF file format mainly store?

A Audio tracks

B Raw images

C Formatted documents

D Executable programs

PDF files store formatted documents that look the same on any device.

Describe what a file extension is and why it is important.

Think about the letters after the dot in a file name.

Explain the difference between changing a file's extension and changing its format.

Consider what happens if you rename a file without converting it.

Practice

1. What does the file extension in a filename tell you?

easy

A. The location of the file on the computer

B. The size of the file in bytes

C. The date the file was created

D. The type of file and which program can open it

Solution

1. Step 1: Understand what a file extension is

   The file extension is the part after the dot in a filename, like .txt or .jpg.

2. Step 2: Know the purpose of the extension

   It tells the computer what type of file it is and which program should open it.

3. Final Answer:

   The type of file and which program can open it -> Option D

4. Quick Check:

   File extension = file type and program [OK]

Hint: File extension shows file type and program [OK]

Common Mistakes:

• Confusing extension with file size
• Thinking extension shows file creation date
• Believing extension shows file location

2. Which of these is the correct way to write a filename with a PDF extension?

easy

A. document.pdf

B. documentpdf

C. document_pdf

D. document-pdf

Solution

1. Step 1: Identify the file extension format

   A file extension always follows a dot after the filename, like .pdf.

2. Step 2: Check the options for correct dot usage

   Only 'document.pdf' uses a dot before 'pdf', making it a valid filename with extension.

3. Final Answer:

   document.pdf -> Option A

4. Quick Check:

   Filename.extension = document.pdf [OK]

Hint: File extension always follows a dot (.) [OK]

Common Mistakes:

• Omitting the dot before the extension
• Using underscores or dashes instead of a dot
• Confusing extension with part of the filename

3. What will happen if you try to open a file named photo.jpeg on a computer?

medium

A. It will open as a text document

B. It will open with a photo or image viewer program

C. It will cause a system error

D. It will open with a music player

Solution

1. Step 1: Recognize the file extension .jpeg

   The .jpeg extension is used for image files, especially photos.

2. Step 2: Understand default program association

   Computers open .jpeg files with image viewer programs, not text editors or music players.

3. Final Answer:

   It will open with a photo or image viewer program -> Option B

4. Quick Check:

   .jpeg = image viewer opens file [OK]

Hint: Match extension to program type (jpeg = image) [OK]

Common Mistakes:

• Thinking .jpeg opens as text
• Assuming .jpeg causes errors
• Confusing image files with audio files

4. A user tries to open a file named report.docx but gets an error. What is the most likely cause?

medium

A. The file size is too large

B. The file extension is missing

C. The program to open .docx files is not installed

D. The file name has spaces

Solution

1. Step 1: Understand the .docx extension

   .docx files are Microsoft Word documents requiring a compatible program to open.

2. Step 2: Identify common error causes

   If the program to open .docx files is missing, the file cannot open, causing an error.

3. Final Answer:

   The program to open .docx files is not installed -> Option C

4. Quick Check:

   Missing program for .docx = error [OK]

Hint: Missing program for extension causes open errors [OK]

Common Mistakes:

• Thinking missing extension causes error
• Blaming file size or spaces in name
• Assuming file is corrupted without checking program

5. You have a text file named notes.txt and want to share it with someone who only has a PDF reader. What should you do?

hard

A. Convert the text file to PDF format before sharing

B. Send the file as is; PDF readers open .txt files automatically

C. Rename the file to notes.pdf without changing content

D. Change the file extension to .docx to make it compatible

Solution

1. Step 1: Understand file format compatibility

   A PDF reader can only open PDF files, not plain text files like .txt.

2. Step 2: Choose the correct way to share

   Renaming the file does not change its format; converting the file to PDF creates a compatible file.

3. Final Answer:

   Convert the text file to PDF format before sharing -> Option A

4. Quick Check:

   Convert format to match reader = success [OK]

Hint: Convert file format, don't just rename extension [OK]

Common Mistakes:

• Renaming extension without converting content
• Assuming PDF readers open all text files
• Changing extension to .docx without conversion