Attachments

Often we just want to type some simple text in a mail message, and we already know almost everything very important that we need to know about that. However, sometimes we would like to "attach" something to a mail message that we send. For example, it could be a text file that contains further information that we would like the recipient to have, or perhaps we would like to send a color image of something with the mail message, or a compiled computer code.

The mailing program allows just such possibilities. Not surprisingly, the command to do this is "Attach", and it can be initiated by clicking on the browser button having this name.

Encoding of Files

Unfortunately, basic email is set up to handle text files (often called "ASCII" files), not the binary files associated with color images or executable computer codes. Thus, we usually cannot send binary files directly in email. The solution to this inconvenience is called encoding: a binary file is "encoded" into ASCII by using a prescription to assign to every possible character in a binary file a unique sequence of printable or ASCII characters. The resulting file is thus a text file (one made only of printable characters) that contains all the information of the binary file in the form of a code using only printable characters. This can then be sent by email, and if on the other end the necessary software exists that can "decode" the encoded file, it can be turned back into the original binary file.

The most common encoding scheme used on Macintoshes is called BinHex. Another encoding scheme, more often found on Unix machines, is called uucode. Thus, to send binary files by email between Macintoshes, one would commonly use BinHex to encode the file on one end, email it, and then use BinHex to decode it on the other end. We discuss the use of BinHex further in a later Exercise and in this Appendix.

General binary files may be encoded using BinHex and attached to email messages. In the example we are going to use here, we will exploit the fact that the mailer associated with the Netscape browser knows automatically how to encode and decode GIF file images. Thus, we can simply attach these to a mail message using the Netscape mailer, and if the person receiving the file is also using Netscape, the file will be automatically decoded on the other end. So in this case we can handle the image-file attachment exactly as if it were a text attachment, even though it is a binary file.

Capturing an Image to a File

To illustrate an attachment in a mail message, we are first going to save an image from the browser into a file, then we are going to mail that file as an attachment to ourselves (it is perfectly legitimate to mail something to yourself; the mail program will be happy to do that. Mailing something to yourself is often a simple way to check how mail programs do various things.)

Go to the top of this page, hold the mouse over the schoolhouse image, and hold the button down. A popup menu like the adjacent figure should appear that gives you several options. Choose the one labeled "Save this Image as". This pops up a dialog box that looks like the figure to the right. Change directories if necessary in this box, and save the image under the name school4_logo.gif on the Desktop. Now you have the image of the schoolhouse in a file on your computer disk.

The Attachment Popup Window

Open the Netscape Mail window, and fill in the "Mail To" field with your email address. Type "attachment test" in the "Subject" window, and leave the "CC:" window blank. Now click on the "Attachment" button. This brings up an Attachment Window. If you click on "Attach File" in this window, a popup menu appears that allows you to select a file somewhere on your computer for attachment. Use this window to choose the file school4_logo.gif that you have just saved to the desktop. The adjacent figure shows the Attachment Window after the file school4_logo.gif has been selected from the Desktop for attachment.

Sending Mail with the Attachment

Once you have attached the documents that you wish to attach, close the Attachment Window. Your main mail window will now look something like this.

If you want to change something before sending, you can edit the addresses and text directly, and you can add or remove attachments by opening the Attachments Window again. Once you are happy with the addresses, message, and attachments, click "SendNow" to mail the message.

Reading the Mail Message

You should receive the message that you sent to yourself rather soon. Once it arrives, use the methods discussed in the previous section to display it. If all has gone well, it should look something like the following image:


As you can see, the message contains both text and the attached image.

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