I have been a Macintosh user for many years. My Windows-based friends send me things called 'zip' files, which my operating system can easily open. They now want me to send them such files and I haven't got a clue what to do. Is there a simple way for me to create these files and send them? Sam, Clear Water Bay DQ: The zip file format, which uses the extension '.zip' or '.ZIP', was designed to compress files so they take up less space and can be stored - or sent to others - more efficiently. Today, many applications also provide some kind of compression. High-speed internet connections have made it much easier to transmit large files. Still, there are many reasons for zip and other file-compression programs to continue to be used. I recently had to send 60 digital pictures to Britain. Although the pictures were already compressed, packing them into a single zip file - which did not compress them further - made life much easier. When the file was decompressed at the other end by the recipient, all the file names were the same as mine. That can sometimes be important. Compression is built into the Mac OS X operating system. If you hold down the 'control' key when you click on the name of a file or a folder, a menu will pop up and one of the entries asks if you would like to 'archive' what you have highlighted. If you click on this option, the system will automatically create a zip file. It is that simple. I have recently been told I should send files in Adobe Systems' portable document format (PDF). I tend to use Microsoft Word. Do I have to buy something else from Adobe? Is it really important for me to be able to do this? Name and address supplied DQ: Adobe's PDF file format is an open standard used by many companies and individuals. One of the main reasons is these files look the same on any platform. If you create a nice-looking document in Microsoft Word with a smart font, it will look utter rubbish on my machine unless I have the same font. PDF files manage this situation far more elegantly. Creating PDF files is relatively easy, depending on your platform. Both the Macintosh and Windows platforms support this file format. When you want to print something in Windows, you can select the option that allows you to 'print to a file' instead of a printer. A complete description of how to do this is at the following site: help.cnet.com/microsoft_word/9602-12576_39-0.html?messageID=2505925&tag=tip-2505925. You can also try a free service on the internet, at www.pdfonline.com . If you have a CV, it is a good idea to have a copy in both Word and PDF formats. Some government offices only accept data in a format freely available and not proprietary, so it is important for you to be able to create PDF files.