Zip it


Zip it
Tip #197/25-May-2005

It’s long been a practice to compress computer files. Compressing files makes them smaller (usually) and allows them to pass around the Internet more easily and securely. In File Formats, Mac Tip #119/17-Sept-2003, I talked about .sit and .hqx formats.

With Mac OS X those formats are almost a thing of the past and we no longer need additional software to compress files. Instead we can do it right from within Mac OS X.

Choose Create Archive from the File menu.

Choose Create Archive from the File menu.

Let’s say you need to e-mail a folder of files, or even a single file, to a friend or colleague.

If you have many files to send it can be useful to put them all in a single folder, but you’ll need to consider how big a file you’re going to attach to your email message.

Try to keep the total file size down below 500 Kilobytes if you’re sending to a someone who uses a modem. If you’re sending to someone on broadband (eg Jetstream or cable) then I’d suggest keeping it below about 3 Megabytes (Mb).

It’s always polite to check that your intended recipient welcomes attachments before just sending them through.

Click once on the file or folder and choose Create Archive from the File menu. After a few moments a new file will appear, with .zip at the end of the filename. You have just “zipped” the file.

I made a folder of 5 photos. That folder was 7.4 Mb in size. I then zipped it and now it was a single file of 7.2 Mb. That would be easier to send as it’s now one file instead of five, but it didn’t actually compress much.

That’s partly to do with how photos work. Really the only way to make photo file sizes smaller is to make the photos themselves smaller. I wouldn’t send an attachment this huge.

Next I made a folder of other files, such as letters, and tried zipping that. This time my file started out at 2.2 Mb and compressed down to 988 Kb. That’s less than half the size of the original.

If you send that to someone using Mac OS X they need only double click it to unzip it. If you send it to a Windows user they will also be able to unzip it as the zip format is very popular for Windows users.

The downside of that popularity is that the Windows world is rife with viruses, trojans and other nasties. Many of these are spread via files which have a .zip in the filename. That has led many organisations and Internet Service Providers to either carefully filter or reject outright files which are zipped.

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