21 Things - Basics

Basics Gold

Files And Domains



Different groups and companies around the world have adopted their own schemes for naming files. They also use special shortcut terms (examples: omg, lol, .jpg, .mp4, etc.). Knowing about filenames, formats, and domains can be very helpful.

Investigation scenario:

Sam Lurk wrote up a CSI science project report on a laptop at home and saved the report with this name: Lurkinvestigation, and turned off the computer.

Sam's teacher emailed that the assignment was late, but no points would be subtracted if the file was emailed immediately.

Sam turned on the computer, and noticed that there were four files named Lurkinvestigation on the desktop.

  • Lurkinvestigation.doc

  • Lurkinvestigation.jpg

  • Lurkinvestigation.xls

  • Lurkinvestigation.mp3.

What to do? Which one was the correct file?

Lurk thought about his class, CSI science investigation, where he took a photo of the crime scene that he inserted into his report, the notes taken as he interviewed a witness, the list of possible suspects he made, and the final written report in his word processing program on his computer. That was a lot of work. Which file name would be his report?


Sam clicked on the Lurkinvestigation.mp3 file and the computer prompt asked what program Sam wanted to use to open the file. Sam didn't know, so he selected Microsoft Word from the list. Error! It wouldn't open the file!

Help! What should Sam Lurk have known and done?

Which file should he have send?

Why would Microsoft Word not open the mp3 file?

Explore File Names below if you need help deciding.

File Names Research

File Names:

A file on the computer (or digital device) needs to have a unique name, or filename to identify it and the program used to create it.

Carefully examine these four filenames. What similarities and differences do you see?

  • aboutme.doc
  • aboutme.pdf
  • aboutme.mp4
  • aboutme.jpg
  • aboutme.docx

Did you notice differences with how many letters and/or numbers come after the period?

*Fact 1: BASE NAME

The first part of the filename before the period is called the base name, and the part after the period is called the file-ending, type, or also the extension.


Companies that create software programs use a unique file-ending (usually 3 or 4 letters after a period) to indicate what type of content it is. Examples include: .doc, .pdf, .jpg, .mp3 

What happened to Sam?

When he clicked on a filename on his computer (or device), it automatically tried to open the program it associated with that file-ending/extension. Sometimes the computer will not know which one to pick and will ask you to decide. 

Caution, Warning, Bad Characters:

Avoid using  the following characters in a filename as it may cause an error or not let you save it: / ? \ % * : | " < > 

Filenames for Images and Photos and Most Popular

File endings for Images and Photos:

When you take photos with your digital camera, use/create artwork, or images (such as avatars, maps, secret images) you are most likely to have files which end with one of these:  .jpg, jpeg, .png, .tif, .bmp, .gif

Popular file endings:

MailBigFiles has compiled a ranking of the most common file extensions which pass through their site for sending large file attachments.  Notice the top 10 most popular extensions used - have you used any of these file types?

When you are trying to locate files on your computer this may help you locate the right kind of file and open it in the correct application.

Here are some other ones you might want to be aware of, especially in creating multimedia projects.

.mp3 and .mp4

.jpg or .jpeg












It is important to notice which domains are being used when researching informational websites. 

What is a domain name? Click here to learn what they are, why they were created, and identify some different ones  (.com, .us, .biz, .gov). As you read through the information, identify which ones might be the most reliable for specific kinds of information.

Visit GoDaddy.com  and make up a possible domain name for yourself to see if it would be available for you to purchase if you wanted to start your own business (besides .com, which are often already taken). 

Class Discussion about Domains:

Tell which domain you think would have the more reliable information and why - .com, .jobs, .me, or .gov? 

If you decided to get your own domain name today, what is available?


Completing this Quest

Using a word processing program:

1. Make a list of five domain name extensions and tell what they mean. (For example: .com = commercial)

2. Make a list of five filename extensions and tell what they mean. (for example: .ppt = PowerPoint)

3. Take the 5 question 9 point quiz. Take a screenshot of your score. 

4. Submit your domain and filename lists and quiz screenshot to your teacher.

Add this Quest to your 21t4s Roadmap as a bonus Quest.

 Return to Basics Gold Quests


ISTE and Common Core Standards

ISTE Standards•S

3. Knowledge Contractor
a. plan and employ effective research strategies to locate information and other resources for their intellectual or creative pursuits

6. Creative Communicator
d. Publish or present content that customizes the message and medium for a variety of audiences

Common Core Standards

CCSS.ELA-Literacy.CCRA.SL.1  Prepare for and participate effectively in a range of conversations and collaborations with diverse partners, building on others’ ideas and expressing their own clearly and persuasively

CCSS.ELA-Literacy.CCRA.SL.2  Integrate and evaluate information presented in diverse media and formats, including visually, quantitatively, and orally