 Welcome to Working with Zip Files. This activity introduces you to what zip files are, their origin, and how to work with them in Windows. A zip file is a compressed container for other files. You can add many files to a zip file, which will be smaller in size than the collective sizes of the files within it. Compression is possible because many files contain whitespace, or bytes of data that are all one character or a set of characters. By removing this whitespace, the file can be compressed. Consider a text file. A text file is made up of lots of words and lots of spaces. Each character has a number from 1 to 255, or the size of one byte. There is a character map called ASCII, which determines what characters are mapped to what number. Characters 1 through 128 are in the printable range, and 129 to 255 are used more for control or metadata. That means most of the characters can be represented with 4 bits rather than 8, resulting in a compressed text file being half the size of an uncompressed one. A zip file is a file where the data has been compressed. Now let's take a look at the origins of zip files, and also how to work with zip files in Windows. Zip files were invented before Windows became popular. In 1987, Phil Katz introduced a DOS-based archival tool called PKARC, which compressed files into a .ARC file, very similar to .zip files. PKARC was an improvement on a DOS program called ARC, which was written in 1985 by Tom Henderson. ARC was the first zip-like program for the PC to become famous. It was used to compress files that were uploaded and downloaded to and from BBSs, or bulletin board systems. PKARC was faster than ARC because it was written in assembler. It was an instant hit. Henderson, who had created PKARC, sued Katz. Katz had taken his PKARC source code and added in data compression algorithms. He renamed the product PKZIP. ZIP was invented to save money. Katz was looking for a way to shorten the amount of time it took to transfer files. In order to transfer files, most people were dialing into BBSs and would be charged long-distance phone rates. The longer the time spent on the line, the more money it would cost. So by compressing files, it took less time and money to transfer the files. Katz never made a lot of money from PKZIP, but the zip format was so popular that it has dominated to this day. Today, zip files are mainly used to group many files together, and the compression feature is seen as a nice bonus. ZIP files are for transport and storage only. You cannot and should not open and work with files directly inside a zip file. Rather, you should unzip first, use the files, and then copy them back into the original zip file, or create a new zip from the edited version. The easiest way to create a zip file in Windows is by using the File Explorer, which you can get to by pressing the Windows key plus E. You can create a zip file from any file or even an entire folder by right-clicking it and selecting Send To, and then Compressed or Zipped Folder. You can add more files to a zip file by simply dragging and dropping files onto it. If the file needs to be nested somewhere in a folder within the zip, there's another step you need to do first. ZIP files are hierarchical, just like folders. Double-click on a zip file to open it up in the File Explorer, and you can navigate the hierarchy just like a file folder. Once you get to the folder you want, you can drag and drop files into it. To remove a file, just double-click on the zip, navigate to the file you want to remove, right-click on it, and select Delete. There is one very important step you must do before you extract files from any zip that you have downloaded from another computer or off the internet. That step is unblocking. By default, Windows is hostile to zip files that come from other computers. They can contain malware and other nasty things. That said, Windows gives you a chance to prove that a downloaded zip is safe. To unblock a zip, right-click on it and select Properties. In the Property window, you will see an Unblock button. Simply press it. Now comes the easy part. To extract the files in a zip file, you can do it the hard way by double-clicking on it, navigating to the file or files you want to extract, and dragging and dropping those files in a folder somewhere. Or you can do it the easy way by right-clicking on the zip file and selecting Extract All. This will create an entirely new folder, and you get to choose where, containing the uncompressed contents of the zip file. In this learning activity, we learned what a zip file is, the origins of zip files, and how to work with zip files in Windows.