The Military Postal History Society (MPHS) offers a number of documents in electronic formats. This web page describes how to extract various documents from a ZIP archive.
File archiving is as old as the Internet. One of the earliest, and longest-lived systems is called ZIP. One or more files are enclosed in a single file, usually with compression to save space and connect time.
The Society offers various electronic documents in ZIP format, both to deliver a number of files at once, as well as to enclose and compress a particular document. When we have ZIPed several files together in one archive, we call it a "website-in-a-box", a configuration that makes it easy to view a particular multipart document using only your web browser without connecting to the internet.
When you are dealing with a ZIP archive, you cannot use the enclosed electronic document(s), unless you first extract all the component files from the ZIP archive. Examples of such ZIP files include:
(You can use the above links for practice.)
First of all, when you see a link, such as those listed above, you want to download the file. The typical way to perform this, is to right-click on the link, and use the "Save As" (or "save link as..") menu item that your browser displays. Be sure to remember where you saved the ZIP file. If you just click on the link, many browsers will offer you the chance to download the file. (Some may offer the option to "Open" the file, while others will immediately download the file.)
Once downloaded, extracting the contents of ZIP files is very easy if you are using the Windows (tm) operating system. Simply double-click on the ".zip" file that you just downloaded. Windows versions after about "95" will automatically display the "Archive" contents to you. Copy the files from the content list of the archive to the desired location on your system. At that point, you can use the enclosed file(s). See the links near the bottom of this page for using those electronic formats.
If you are not using Windows, you can still extract ZIP archive contents. There is a very good free product called 7ZIP, which has been released for a wide variety of phones, tablets, and computer systems. Download and use that product (or App) to extract the ZIP contents. You can get a free copy of 7ZIP from the website 7ZIP Download. Near the bottom of the web page are listed the non-Windows systems for which you can get a free copy of 7ZIP. Follow their installation instructions. Use your App "store" on the phone or tablet to get the 7ZIP App for your particular device.
NOTE: There is one more "format" we are using, which we call "website-in-a-box". The Al Kugel link above contains a set of files that make up a stand-alone web page containing his exhibit contents. To view the exhibit, you extract the entire ZIP contents into a new, empty, folder (directory) on your computer, phone, or tablet. Then, make your web browser open the "index.html" file in that group of files. (This is usually the "Open" menu selection.) Your browser will then become the document "reader" as you view Al's award-winning exhibit. You do not need to be connected to the internet, and you do not need any special viewer tool, aside from your browser. There are several such packages stored on the Society's website, and they will be identified as such.