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Opening Files with Different File Formats

Warning: Always proceed with caution when opening a file, even from someone you know and especially if you weren't expecting it. Computer viruses, worms, or trojans are often transmitted this way.

If you receive a suspicious file, you should verify that the person who appears to have sent it to you actually did intend to send it. The From information in an e-mail message can be easily forged to look like it came from someone you know.

If you cannot verify that the file was purposely sent to you, and you are going to open it anyway, first make sure your antivirus definitions are up-to-date and that you have all of the patches to your computer's operating system installed. Once you have done that, then scan the file with your antivirus application. The antivirus scan should happen quickly and you should be able to see if any threats were identified.

Are There Any Universal File Formats?

There are some. For example, any word processor can read a 'text' or .txt file, and almost any word processor can read RTF (Rich Text Format) files. Keep in mind, though, that if you use the RTF format, you may lose some formatting in the translation process. Similarly, any graphics program should be able to open a TIFF or a JPEG file. Acrobat Reader can open a PDF file. You can often use these universal file formats to move data between programs that cannot otherwise read each other's files.

Many widely-used applications (such as Microsoft Office) are available for use on the Macintosh or Windows platforms. These applications can read files created by the same application on the other operating system. Some of these "cross-platform" applications include Adobe Reader and PageMaker; Microsoft Word, Excel, and PowerPoint; WordPerfect;  and FileMaker Pro.

Macintosh and Windows machines rely on file-typing to determine which application opens when a document is double-clicked. Windows relies entirely on three-letter filename extensions (for example: ".doc", ".xls", ".ppt", etc.), whereas the Macintosh operating system uses hidden, four-letter type and creator codes for every file. Hence, if you are moving from a Macintosh PC to a Windows PC, running your files through a program such as Conversions Plus may rectify the differences in file typing.

How Do I Open a File I Didn't Create?

The format you receive the file in may work with an application you currently have, or you may need to "translate" the file into a different format.

If you have the application used to create the file, start that application, then use the Open command from the File menu to open the file, rather than double-clicking the file icon.

Most programs have some built-in translators (sometimes referred to as filters) that convert files to and from various formats. Some software companies provide translators that can be added to their programs. To locate add-on translators, refer to the "support" page at the vendor's Web site.

If you are using a Macintosh and you don't know what application created the file, and double-clicking on it doesn't open it, select the document and select Get Info from the File menu. The window that appears may tell you what application created the file. Or you may have to contact the person who sent it to you.

If you are using a Windows computer and you don't know what application created the file, and double-clicking on it doesn't work, the file extension (what appears after the period in the file name) may provide some clue as to what type of file it is. You can right-click Start, then click Explore to open Windows Explorer. From the Menu bar, select Tools, then Folder Options, then click the File Types tab. From here, you can see which application is trying to open this type of a file. Or, another way of determining what program was used to create a files is to search for the file extension at

If you still can't open the file, contact the person who sent it to you and ask them to send it again, possibly in a different file type.

How Can I Open a File That Was Created with an Application I Don't Have?

If you receive a file that was created by a program you don't have and it can't be opened using the programs you do have, check the Software Downloads page on the Web. The KeyServer provides access to a variety of commercial applications that could provide you with the program you need to open the file. If not, the vendor whose software made the file may have a reader plug-in that can be installed on your computer to open and view the file. If none of these options are successful, ask the sender to resend the file to you in RTF (Rich Text Format), plain text, or PDF format. 

What If I Need to Send a File to Someone That I Know Doesn't Have the Application the File Was Created In?

Many applications provide the ability to save a file in a different format. This is usually found under the Save As command in the File menu. Find out what applications and versions the person to whom you are sending the file has, then see if you can save the file in the appropriate format for that application. If that option is not available, the vendor whose software made the file may have a reader plug-in that can be installed on the recipient's computer to open and view the file.  Finally, you can try saving it as "rich text format" (RTF), or as a simple text file. To preserve formatting and graphics, save the file as a PDF.

How Can I Open a File That Was Received As an E-mail Enclosure?

Many people "compress" files before sending them as enclosures with an e-mail message. Compressing a file essentially removes empty spaces in the file so that the actual file size is smaller, and therefore, takes less time to send. If you receive a file via e-mail as an enclosure, it may have a .zip, .hqx, or .sit extension on the end of the file name. To decompress the file, save it to your computer, then use a utility such as StuffIt Expander to decompress the file.

If you receive an e-mail message that was supposed to have an enclosure in it, but instead there is a large section of seemingly random characters in the message, it may be that the compressed file didn't get decompressed properly when it was received into your mailbox.  What you can do is, close the message, then from the In Box, highlight the message and select Save Message from the File menu. Save the message to your computer. Start StuffIt Expander, then drag the file you want to uncompress onto the Expander window. Once the file is uncompressed, see How Do I Open a File I Didn't Create?.

Sometimes you may receive an e-mail where you cannot open the enclosure within e-mail, or the size of the e-mail indicates that an enclosure should be attached but one doesn't appear to be. If you cannot open the enclosure or cannot find the enclosure, try opening the e-mail message in BWA or OWA.

Dartmouth uses a program available for both Windows and Macintosh computers developed by Aladdin Systems, Inc. to uncompress files known as StuffIt Expander. It can be downloaded from the General Productivity sections of the Dartmouth Software Downloads web pages.

How Can I Exchange Files Between a Macintosh and a Windows Computer?

By E-mail: This is the most common and often proves to be the easiest method of exchanging files that are not extremely large.

Removable media: CDs, DVDs, External Hard Drives, Flash Drives, etc. can be useful means of sharing files, especially if the computers aren't connected to a network or the Internet.

Over networks via file sharing: Windows 7 and Mac OS X can share files directly as the Mac OS X operating system supports both Windows file sharing protocol (SMB) and File Transfer protocol (FTP) over TCP/IP. For more information on file sharing, see Safe File Sharing.

By FTP (File Transfer Protocol): The computers do not have to be near each other or even on the same network, and you do not have to purchase any additional software. You do, however, need access to an FTP server. Follow the instructions for Using a File Transfer Protocol (FTP) Program.

Are There Other Utilities I Can Use to Open Files on My Computer?

Macintosh users who frequently need to open a wide variety of file formats may want to purchase a copy of MacLink Plus Deluxe (DataViz Corporation) and keep it up to date. This is the best tool for dealing with unanticipated file formats. Conversions Plus is a similar conversion utility for Windows computers. Both can be purchased from The Computer Store (McNutt Hall).

Last Updated: 11/4/14