Answer:
Files have a two part name. Names of them are like document.doc, bulletin.pdf and calc.exe They have a part that is the specific name of the file (the first part and a last name (or extension) that tells us the program it is associated with. Last names of doc or docx are normally associated with Word (docx with word 2007), pdf is with Adobe Acrobat and exe is a program you can run (calc.exe is the calculator in windows.

By default Windows hides known file extensions (last names) or the ones it knows the applications the file is associated with. This makes the listing of files easier to read document, bulletin, and calc but you only know application/program it is associated with by looking at the icon/little picture by it. You can change your setting to see all extensions. I will describe in a different column. Besides not seeing it, people wanting to get people to run bad programs will put two extensions and the first shows and you think it is that. For instance call it picture.jpg.exe and it shows as picture.jpg and people click to open a picture and actually it is a program that runs usually a virus.

There are times to change an extension. Sometimes you want to load or submit a file somewhere and the program does not allow that file type. For instance in many online education programs students can not upload .php or .pka or .html files. The solution is to right click on the file name and choose rename and then you can type a new name. The best thing is first hit the forward arrow so the whole is not highlighted (if you do not when you type a character or backspace the existing name disappears. If you forgot what it was hit ESC and you will cancel out and have the old name again) and then back space off the extension/last name and type the new one. Then press ENTER.

Be careful changing file extensions as you can mess up the computer. Don’t change files with extensions of sys or dll.

Changing the file extension does not change the type of file, just what it appears to be. Changing jpg to gif will not make a jpg picture a gif picture and most programs will give you errors when you try to use that file. However there are times that you may need to change an file name extension.

Send me your questions about computers to me at the paper or to my e-mail dwight@dwightwatt.com and tell me you read this in the paper. I will pick a question to answer each week.