PDF File Format
PDF stands for Portable Document Format. This is a very common format for documents available on the internet. The advantage of the PDF format is that you can be almost 100% guaranteed that you will be able to view and print out the document in the same format it is supposed to be, without having to worry about what type of computer you have (Mac or IBM) or what fonts you have. Complicated layouts, such as multiple columns, tables, and even images, will all be preserved in PDF format. The disadvantage of the PDF format is that you have to get a separate program to open the PDF file, because word processors such as MS Word or Word Perfect can not open PDF files. But the good news is that this special program, called the Adobe Acrobat Reader, is free and there are versions for both the Macintosh and IBM.
To make files smaller so that they will download faster, many files on the internet are compressed. One common format of compressed files is the zip format. When you save a zipped to your hard drive, you have to unzip it before you can use it (i.e., before you can open it in a word processor, graphics program, etc.) Zipped files can be uncompressed with WinZip (IBM) or ZipIt (Mac), two shareware programs that are available from http://www.shareware.com.